diff --git a/launcher/RuntimeContext.h b/launcher/RuntimeContext.h
index 767857285..d98d407f6 100644
--- a/launcher/RuntimeContext.h
+++ b/launcher/RuntimeContext.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <QSet>
 #include <QString>
 #include "settings/SettingsObject.h"
 
@@ -7,6 +8,7 @@ struct RuntimeContext {
     QString javaArchitecture;
     QString javaRealArchitecture;
     QString javaPath;
+    QString system;
 
     QString mappedJavaRealArchitecture() const {
         if (javaRealArchitecture == "aarch64") {
@@ -19,6 +21,27 @@ struct RuntimeContext {
         javaArchitecture = instanceSettings->get("JavaArchitecture").toString();
         javaRealArchitecture = instanceSettings->get("JavaRealArchitecture").toString();
         javaPath = instanceSettings->get("JavaPath").toString();
+        system = currentSystem();
+    }
+
+    QString getClassifier() const {
+        return system + "-" + mappedJavaRealArchitecture();
+    }
+
+    // "Legacy" refers to the fact that Mojang assumed that these are the only two architectures
+    bool isLegacyArch() const {
+        QSet<QString> legacyArchitectures{"amd64", "x86_64", "i686"};
+        return legacyArchitectures.contains(mappedJavaRealArchitecture());
+    }
+
+    bool classifierMatches(QString target) const {
+        // try to match precise classifier "[os]-[arch]"
+        bool x = target == getClassifier();
+        // try to match imprecise classifier on legacy architectures "[os]"
+        if (!x && isLegacyArch())
+            x = target == system;
+
+        return x;
     }
 
     static QString currentSystem() {
diff --git a/launcher/minecraft/Library.cpp b/launcher/minecraft/Library.cpp
index 1689e27c8..42a42d87b 100644
--- a/launcher/minecraft/Library.cpp
+++ b/launcher/minecraft/Library.cpp
@@ -112,9 +112,9 @@ QList<NetAction::Ptr> Library::getDownloads(
     {
         if(isNative())
         {
-            if(m_nativeClassifiers.contains(runtimeContext.currentSystem()))
+            auto nativeClassifier = getCompatibleNative(runtimeContext);
+            if(!nativeClassifier.isNull())
             {
-                auto nativeClassifier = m_nativeClassifiers[runtimeContext.currentSystem()];
                 if(nativeClassifier.contains("${arch}"))
                 {
                     auto nat32Classifier = nativeClassifier;
@@ -215,7 +215,7 @@ bool Library::isActive(const RuntimeContext & runtimeContext) const
         RuleAction ruleResult = Disallow;
         for (auto rule : m_rules)
         {
-            RuleAction temp = rule->apply(this);
+            RuleAction temp = rule->apply(this, runtimeContext);
             if (temp != Defer)
                 ruleResult = temp;
         }
@@ -223,7 +223,7 @@ bool Library::isActive(const RuntimeContext & runtimeContext) const
     }
     if (isNative())
     {
-        result = result && m_nativeClassifiers.contains(runtimeContext.currentSystem());
+        result = result && !getCompatibleNative(runtimeContext).isNull();
     }
     return result;
 }
@@ -238,6 +238,19 @@ bool Library::isAlwaysStale() const
     return m_hint == "always-stale";
 }
 
+QString Library::getCompatibleNative(const RuntimeContext & runtimeContext) const {
+    // try to match precise classifier "[os]-[arch]"
+    auto entry = m_nativeClassifiers.constFind(runtimeContext.getClassifier());
+    // try to match imprecise classifier on legacy architectures "[os]"
+    if (entry == m_nativeClassifiers.constEnd() && runtimeContext.isLegacyArch())
+        entry = m_nativeClassifiers.constFind(runtimeContext.system);
+
+    if (entry == m_nativeClassifiers.constEnd())
+        return QString();
+
+    return entry.value();
+}
+
 void Library::setStoragePrefix(QString prefix)
 {
     m_storagePrefix = prefix;
@@ -271,9 +284,10 @@ QString Library::filename(const RuntimeContext & runtimeContext) const
 
     // otherwise native, override classifiers. Mojang HACK!
     GradleSpecifier nativeSpec = m_name;
-    if (m_nativeClassifiers.contains(runtimeContext.currentSystem()))
+    QString nativeClassifier = getCompatibleNative(runtimeContext);
+    if (!nativeClassifier.isNull())
     {
-        nativeSpec.setClassifier(m_nativeClassifiers[runtimeContext.currentSystem()]);
+        nativeSpec.setClassifier(nativeClassifier);
     }
     else
     {
@@ -299,9 +313,10 @@ QString Library::storageSuffix(const RuntimeContext & runtimeContext) const
 
     // otherwise native, override classifiers. Mojang HACK!
     GradleSpecifier nativeSpec = m_name;
-    if (m_nativeClassifiers.contains(runtimeContext.currentSystem()))
+    QString nativeClassifier = getCompatibleNative(runtimeContext);
+    if (!nativeClassifier.isNull())
     {
-        nativeSpec.setClassifier(m_nativeClassifiers[runtimeContext.currentSystem()]);
+        nativeSpec.setClassifier(nativeClassifier);
     }
     else
     {
diff --git a/launcher/minecraft/Library.h b/launcher/minecraft/Library.h
index e0432fb85..b8fae9eca 100644
--- a/launcher/minecraft/Library.h
+++ b/launcher/minecraft/Library.h
@@ -3,6 +3,7 @@
 #include <net/NetAction.h>
 #include <QPair>
 #include <QList>
+#include <QString>
 #include <QStringList>
 #include <QMap>
 #include <QDir>
@@ -155,6 +156,8 @@ public: /* methods */
     QList<NetAction::Ptr> getDownloads(const RuntimeContext & runtimeContext, class HttpMetaCache * cache,
                                      QStringList & failedLocalFiles, const QString & overridePath) const;
 
+    QString getCompatibleNative(const RuntimeContext & runtimeContext) const;
+
 private: /* methods */
     /// the default storage prefix used by PolyMC
     static QString defaultStoragePrefix();
diff --git a/launcher/minecraft/Rule.h b/launcher/minecraft/Rule.h
index 2ed49d78c..4c75cee42 100644
--- a/launcher/minecraft/Rule.h
+++ b/launcher/minecraft/Rule.h
@@ -37,7 +37,7 @@ class Rule
 {
 protected:
     RuleAction m_result;
-    virtual bool applies(const Library *parent) = 0;
+    virtual bool applies(const Library *parent, const RuntimeContext & runtimeContext) = 0;
 
 public:
     Rule(RuleAction result) : m_result(result)
@@ -45,9 +45,9 @@ public:
     }
     virtual ~Rule() {};
     virtual QJsonObject toJson() = 0;
-    RuleAction apply(const Library *parent)
+    RuleAction apply(const Library *parent, const RuntimeContext & runtimeContext)
     {
-        if (applies(parent))
+        if (applies(parent, runtimeContext))
             return m_result;
         else
             return Defer;
@@ -63,9 +63,9 @@ private:
     QString m_version_regexp;
 
 protected:
-    virtual bool applies(const Library *)
+    virtual bool applies(const Library *, const RuntimeContext & runtimeContext)
     {
-        return (m_system == RuntimeContext::currentSystem());
+        return runtimeContext.classifierMatches(m_system);
     }
     OsRule(RuleAction result, QString system, QString version_regexp)
         : Rule(result), m_system(system), m_version_regexp(version_regexp)
@@ -84,7 +84,7 @@ public:
 class ImplicitRule : public Rule
 {
 protected:
-    virtual bool applies(const Library *)
+    virtual bool applies(const Library *, const RuntimeContext & runtimeContext)
     {
         return true;
     }
diff --git a/tests/Library_test.cpp b/tests/Library_test.cpp
index a4ca92325..b9027e120 100644
--- a/tests/Library_test.cpp
+++ b/tests/Library_test.cpp
@@ -5,6 +5,7 @@
 #include <minecraft/Library.h>
 #include <net/HttpMetaCache.h>
 #include <FileSystem.h>
+#include <RuntimeContext.h>
 
 class LibraryTest : public QObject
 {
@@ -24,6 +25,14 @@ private:
     {
         return {FS::PathCombine(cache->getBasePath("libraries"), relative)};
     }
+
+    RuntimeContext dummyContext(QString system = "linux", QString arch = "64", QString realArch = "amd64") {
+        RuntimeContext r;
+        r.javaArchitecture = arch;
+        r.javaRealArchitecture = realArch;
+        r.system = system;
+        return r;
+    }
 private
 slots:
     void initTestCase()
@@ -34,12 +43,13 @@ slots:
     }
     void test_legacy()
     {
+        RuntimeContext r = dummyContext();
         Library test("test.package:testname:testversion");
         QCOMPARE(test.artifactPrefix(), QString("test.package:testname"));
         QCOMPARE(test.isNative(), false);
 
         QStringList jar, native, native32, native64;
-        test.getApplicableFiles(currentSystem, jar, native, native32, native64, QString());
+        test.getApplicableFiles(r, jar, native, native32, native64, QString());
         QCOMPARE(jar, getStorage("test/package/testname/testversion/testname-testversion.jar"));
         QCOMPARE(native, {});
         QCOMPARE(native32, {});
@@ -47,10 +57,11 @@ slots:
     }
     void test_legacy_url()
     {
+        RuntimeContext r = dummyContext();
         QStringList failedFiles;
         Library test("test.package:testname:testversion");
         test.setRepositoryURL("file://foo/bar");
-        auto downloads = test.getDownloads(currentSystem, cache.get(), failedFiles, QString());
+        auto downloads = test.getDownloads(r, cache.get(), failedFiles, QString());
         QCOMPARE(downloads.size(), 1);
         QCOMPARE(failedFiles, {});
         NetAction::Ptr dl = downloads[0];
@@ -58,27 +69,29 @@ slots:
     }
     void test_legacy_url_local_broken()
     {
+        RuntimeContext r = dummyContext();
         Library test("test.package:testname:testversion");
         QCOMPARE(test.isNative(), false);
         QStringList failedFiles;
         test.setHint("local");
-        auto downloads = test.getDownloads(currentSystem, cache.get(), failedFiles, QString());
+        auto downloads = test.getDownloads(r, cache.get(), failedFiles, QString());
         QCOMPARE(downloads.size(), 0);
         QCOMPARE(failedFiles, {"testname-testversion.jar"});
     }
     void test_legacy_url_local_override()
     {
+        RuntimeContext r = dummyContext();
         Library test("com.paulscode:codecwav:20101023");
         QCOMPARE(test.isNative(), false);
         QStringList failedFiles;
         test.setHint("local");
-        auto downloads = test.getDownloads(currentSystem, cache.get(), failedFiles, QFINDTESTDATA("testdata/Library"));
+        auto downloads = test.getDownloads(r, cache.get(), failedFiles, QFINDTESTDATA("testdata/Library"));
         QCOMPARE(downloads.size(), 0);
         qDebug() << failedFiles;
         QCOMPARE(failedFiles.size(), 0);
 
         QStringList jar, native, native32, native64;
-        test.getApplicableFiles(currentSystem, jar, native, native32, native64, QFINDTESTDATA("testdata/Library"));
+        test.getApplicableFiles(r, jar, native, native32, native64, QFINDTESTDATA("testdata/Library"));
         QCOMPARE(jar, {QFileInfo(QFINDTESTDATA("testdata/Library/codecwav-20101023.jar")).absoluteFilePath()});
         QCOMPARE(native, {});
         QCOMPARE(native32, {});
@@ -86,19 +99,20 @@ slots:
     }
     void test_legacy_native()
     {
+        RuntimeContext r = dummyContext();
         Library test("test.package:testname:testversion");
         test.m_nativeClassifiers["linux"] = "linux";
         QCOMPARE(test.isNative(), true);
         test.setRepositoryURL("file://foo/bar");
         {
             QStringList jar, native, native32, native64;
-            test.getApplicableFiles(Os_Linux, jar, native, native32, native64, QString());
+            test.getApplicableFiles(r, jar, native, native32, native64, QString());
             QCOMPARE(jar, {});
             QCOMPARE(native, getStorage("test/package/testname/testversion/testname-testversion-linux.jar"));
             QCOMPARE(native32, {});
             QCOMPARE(native64, {});
             QStringList failedFiles;
-            auto dls = test.getDownloads(Os_Linux, cache.get(), failedFiles, QString());
+            auto dls = test.getDownloads(r, cache.get(), failedFiles, QString());
             QCOMPARE(dls.size(), 1);
             QCOMPARE(failedFiles, {});
             auto dl = dls[0];
@@ -107,6 +121,7 @@ slots:
     }
     void test_legacy_native_arch()
     {
+        RuntimeContext r = dummyContext();
         Library test("test.package:testname:testversion");
         test.m_nativeClassifiers["linux"]="linux-${arch}";
         test.m_nativeClassifiers["osx"]="osx-${arch}";
@@ -115,41 +130,43 @@ slots:
         test.setRepositoryURL("file://foo/bar");
         {
             QStringList jar, native, native32, native64;
-            test.getApplicableFiles(Os_Linux, jar, native, native32, native64, QString());
+            test.getApplicableFiles(r, jar, native, native32, native64, QString());
             QCOMPARE(jar, {});
             QCOMPARE(native, {});
             QCOMPARE(native32, getStorage("test/package/testname/testversion/testname-testversion-linux-32.jar"));
             QCOMPARE(native64, getStorage("test/package/testname/testversion/testname-testversion-linux-64.jar"));
             QStringList failedFiles;
-            auto dls = test.getDownloads(Os_Linux, cache.get(), failedFiles, QString());
+            auto dls = test.getDownloads(r, cache.get(), failedFiles, QString());
             QCOMPARE(dls.size(), 2);
             QCOMPARE(failedFiles, {});
             QCOMPARE(dls[0]->m_url, QUrl("file://foo/bar/test/package/testname/testversion/testname-testversion-linux-32.jar"));
             QCOMPARE(dls[1]->m_url, QUrl("file://foo/bar/test/package/testname/testversion/testname-testversion-linux-64.jar"));
         }
+        r.system = "windows";
         {
             QStringList jar, native, native32, native64;
-            test.getApplicableFiles(Os_Windows, jar, native, native32, native64, QString());
+            test.getApplicableFiles(r, jar, native, native32, native64, QString());
             QCOMPARE(jar, {});
             QCOMPARE(native, {});
             QCOMPARE(native32, getStorage("test/package/testname/testversion/testname-testversion-windows-32.jar"));
             QCOMPARE(native64, getStorage("test/package/testname/testversion/testname-testversion-windows-64.jar"));
             QStringList failedFiles;
-            auto dls = test.getDownloads(Os_Windows, cache.get(), failedFiles, QString());
+            auto dls = test.getDownloads(r, cache.get(), failedFiles, QString());
             QCOMPARE(dls.size(), 2);
             QCOMPARE(failedFiles, {});
             QCOMPARE(dls[0]->m_url, QUrl("file://foo/bar/test/package/testname/testversion/testname-testversion-windows-32.jar"));
             QCOMPARE(dls[1]->m_url, QUrl("file://foo/bar/test/package/testname/testversion/testname-testversion-windows-64.jar"));
         }
+        r.system = "osx";
         {
             QStringList jar, native, native32, native64;
-            test.getApplicableFiles(Os_OSX, jar, native, native32, native64, QString());
+            test.getApplicableFiles(r, jar, native, native32, native64, QString());
             QCOMPARE(jar, {});
             QCOMPARE(native, {});
             QCOMPARE(native32, getStorage("test/package/testname/testversion/testname-testversion-osx-32.jar"));
             QCOMPARE(native64, getStorage("test/package/testname/testversion/testname-testversion-osx-64.jar"));
             QStringList failedFiles;
-            auto dls = test.getDownloads(Os_OSX, cache.get(), failedFiles, QString());
+            auto dls = test.getDownloads(r, cache.get(), failedFiles, QString());
             QCOMPARE(dls.size(), 2);
             QCOMPARE(failedFiles, {});
             QCOMPARE(dls[0]->m_url, QUrl("file://foo/bar/test/package/testname/testversion/testname-testversion-osx-32.jar"));
@@ -158,6 +175,7 @@ slots:
     }
     void test_legacy_native_arch_local_override()
     {
+        RuntimeContext r = dummyContext();
         Library test("test.package:testname:testversion");
         test.m_nativeClassifiers["linux"]="linux-${arch}";
         test.setHint("local");
@@ -165,96 +183,104 @@ slots:
         test.setRepositoryURL("file://foo/bar");
         {
             QStringList jar, native, native32, native64;
-            test.getApplicableFiles(Os_Linux, jar, native, native32, native64, QFINDTESTDATA("testdata/Library"));
+            test.getApplicableFiles(r, jar, native, native32, native64, QFINDTESTDATA("testdata/Library"));
             QCOMPARE(jar, {});
             QCOMPARE(native, {});
             QCOMPARE(native32, {QFileInfo(QFINDTESTDATA("testdata/Library/testname-testversion-linux-32.jar")).absoluteFilePath()});
             QCOMPARE(native64, {QFileInfo(QFINDTESTDATA("testdata/Library") + "/testname-testversion-linux-64.jar").absoluteFilePath()});
             QStringList failedFiles;
-            auto dls = test.getDownloads(Os_Linux, cache.get(), failedFiles, QFINDTESTDATA("testdata/Library"));
+            auto dls = test.getDownloads(r, cache.get(), failedFiles, QFINDTESTDATA("testdata/Library"));
             QCOMPARE(dls.size(), 0);
             QCOMPARE(failedFiles, {QFileInfo(QFINDTESTDATA("testdata/Library") + "/testname-testversion-linux-64.jar").absoluteFilePath()});
         }
     }
     void test_onenine()
     {
+        RuntimeContext r = dummyContext("osx");
         auto test = readMojangJson(QFINDTESTDATA("testdata/Library/lib-simple.json"));
         {
             QStringList jar, native, native32, native64;
-            test->getApplicableFiles(Os_OSX, jar, native, native32, native64, QString());
+            test->getApplicableFiles(r, jar, native, native32, native64, QString());
             QCOMPARE(jar, getStorage("com/paulscode/codecwav/20101023/codecwav-20101023.jar"));
             QCOMPARE(native, {});
             QCOMPARE(native32, {});
             QCOMPARE(native64, {});
         }
+        r.system = "linux";
         {
             QStringList failedFiles;
-            auto dls = test->getDownloads(Os_Linux, cache.get(), failedFiles, QString());
+            auto dls = test->getDownloads(r, cache.get(), failedFiles, QString());
             QCOMPARE(dls.size(), 1);
             QCOMPARE(failedFiles, {});
             QCOMPARE(dls[0]->m_url, QUrl("https://libraries.minecraft.net/com/paulscode/codecwav/20101023/codecwav-20101023.jar"));
         }
+        r.system = "osx";
         test->setHint("local");
         {
             QStringList jar, native, native32, native64;
-            test->getApplicableFiles(Os_OSX, jar, native, native32, native64, QFINDTESTDATA("testdata/Library"));
+            test->getApplicableFiles(r, jar, native, native32, native64, QFINDTESTDATA("testdata/Library"));
             QCOMPARE(jar, {QFileInfo(QFINDTESTDATA("testdata/Library/codecwav-20101023.jar")).absoluteFilePath()});
             QCOMPARE(native, {});
             QCOMPARE(native32, {});
             QCOMPARE(native64, {});
         }
+        r.system = "linux";
         {
             QStringList failedFiles;
-            auto dls = test->getDownloads(Os_Linux, cache.get(), failedFiles, QFINDTESTDATA("testdata/Library"));
+            auto dls = test->getDownloads(r, cache.get(), failedFiles, QFINDTESTDATA("testdata/Library"));
             QCOMPARE(dls.size(), 0);
             QCOMPARE(failedFiles, {});
         }
     }
     void test_onenine_local_override()
     {
+        RuntimeContext r = dummyContext("osx");
         auto test = readMojangJson(QFINDTESTDATA("testdata/Library/lib-simple.json"));
         test->setHint("local");
         {
             QStringList jar, native, native32, native64;
-            test->getApplicableFiles(Os_OSX, jar, native, native32, native64, QFINDTESTDATA("testdata/Library"));
+            test->getApplicableFiles(r, jar, native, native32, native64, QFINDTESTDATA("testdata/Library"));
             QCOMPARE(jar, {QFileInfo(QFINDTESTDATA("testdata/Library/codecwav-20101023.jar")).absoluteFilePath()});
             QCOMPARE(native, {});
             QCOMPARE(native32, {});
             QCOMPARE(native64, {});
         }
+        r.system = "linux";
         {
             QStringList failedFiles;
-            auto dls = test->getDownloads(Os_Linux, cache.get(), failedFiles, QFINDTESTDATA("testdata/Library"));
+            auto dls = test->getDownloads(r, cache.get(), failedFiles, QFINDTESTDATA("testdata/Library"));
             QCOMPARE(dls.size(), 0);
             QCOMPARE(failedFiles, {});
         }
     }
     void test_onenine_native()
     {
+        RuntimeContext r = dummyContext("osx");
         auto test = readMojangJson(QFINDTESTDATA("testdata/Library/lib-native.json"));
         QStringList jar, native, native32, native64;
-        test->getApplicableFiles(Os_OSX, jar, native, native32, native64, QString());
+        test->getApplicableFiles(r, jar, native, native32, native64, QString());
         QCOMPARE(jar, QStringList());
         QCOMPARE(native, getStorage("org/lwjgl/lwjgl/lwjgl-platform/2.9.4-nightly-20150209/lwjgl-platform-2.9.4-nightly-20150209-natives-osx.jar"));
         QCOMPARE(native32, {});
         QCOMPARE(native64, {});
         QStringList failedFiles;
-        auto dls = test->getDownloads(Os_OSX, cache.get(), failedFiles, QString());
+        auto dls = test->getDownloads(r, cache.get(), failedFiles, QString());
         QCOMPARE(dls.size(), 1);
         QCOMPARE(failedFiles, {});
         QCOMPARE(dls[0]->m_url, QUrl("https://libraries.minecraft.net/org/lwjgl/lwjgl/lwjgl-platform/2.9.4-nightly-20150209/lwjgl-platform-2.9.4-nightly-20150209-natives-osx.jar"));
     }
     void test_onenine_native_arch()
     {
+        RuntimeContext r = dummyContext("windows");
         auto test = readMojangJson(QFINDTESTDATA("testdata/Library/lib-native-arch.json"));
         QStringList jar, native, native32, native64;
-        test->getApplicableFiles(Os_Windows, jar, native, native32, native64, QString());
+        test->getApplicableFiles(r, jar, native, native32, native64, QString());
         QCOMPARE(jar, {});
         QCOMPARE(native, {});
         QCOMPARE(native32, getStorage("tv/twitch/twitch-platform/5.16/twitch-platform-5.16-natives-windows-32.jar"));
         QCOMPARE(native64, getStorage("tv/twitch/twitch-platform/5.16/twitch-platform-5.16-natives-windows-64.jar"));
         QStringList failedFiles;
-        auto dls = test->getDownloads(Os_Windows, cache.get(), failedFiles, QString());
+        auto dls = test->getDownloads(r, cache.get(), failedFiles, QString());
         QCOMPARE(dls.size(), 2);
         QCOMPARE(failedFiles, {});
         QCOMPARE(dls[0]->m_url, QUrl("https://libraries.minecraft.net/tv/twitch/twitch-platform/5.16/twitch-platform-5.16-natives-windows-32.jar"));