diff --git a/lib/IRGen/IRGenModule.cpp b/lib/IRGen/IRGenModule.cpp
index b936bf123ec..83e72c05908 100644
--- a/lib/IRGen/IRGenModule.cpp
+++ b/lib/IRGen/IRGenModule.cpp
@@ -817,6 +817,8 @@ llvm::AttributeSet IRGenModule::constructInitialAttributes() {
   std::vector<std::string> &Features = ClangOpts.Features;
   if (!Features.empty()) {
     SmallString<64> allFeatures;
+    // Sort so that the target features string is canonical.
+    std::sort(Features.begin(), Features.end());
     interleave(Features, [&](const std::string &s) {
       allFeatures.append(s);
     }, [&]{
diff --git a/test/IRGen/ordering_x86.sil b/test/IRGen/ordering_x86.sil
index ddae69d4a0f..c83e803db77 100644
--- a/test/IRGen/ordering_x86.sil
+++ b/test/IRGen/ordering_x86.sil
@@ -2,6 +2,7 @@
 // RUN: %swift -target i386-apple-ios7.1 %s -module-name main -emit-ir -o - | %FileCheck %s
 // RUN: %swift -target x86_64-apple-ios7.1 %s -module-name main -emit-ir -o - | %FileCheck %s
 // RUN: %swift -target x86_64-unknown-linux-gnu -disable-objc-interop %s -module-name main -emit-ir -o - | %FileCheck %s
+// RUN: %swift -target x86_64-apple-macosx10.9 -module-name main %s -emit-ir -o - | %FileCheck %s --check-prefix=X86_64
 
 // REQUIRES: CODEGENERATOR=X86
 
@@ -34,3 +35,10 @@ bb0:
 // CHECK: define{{( protected)?}} swiftcc void @foo
 // CHECK: define{{( protected)?}} swiftcc void @bar
 // CHECK: define{{( protected)?}} swiftcc void @baz
+
+// Make sure that the target features are ordered. We care because function
+// merging does not identify two otherwise identical functions as the same if
+// the order of features differs.
+
+// X86_64: define{{( protected)?}} swiftcc void @baz{{.*}}#0
+// X86_64: #0 = {{.*}}"target-features"="+cx16,+fxsr,+mmx,+sse,+sse2,+sse3,+ssse3,+x87"