diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
index a9fcee7c98c..3d40c126dd2 100644
--- a/lib/Linker/LinkModules.cpp
+++ b/lib/Linker/LinkModules.cpp
@@ -1050,7 +1050,12 @@ bool ModuleLinker::shouldLinkFromSource(bool &LinkFromSrc,
       return false;
     }
     // If the Dest is weak, use the source linkage.
-    LinkFromSrc = Dest.hasExternalWeakLinkage();
+    if (Dest.hasExternalWeakLinkage()) {
+      LinkFromSrc = true;
+      return false;
+    }
+    // Link an available_externally over a declaration.
+    LinkFromSrc = !Src.isDeclaration() && Dest.isDeclaration();
     return false;
   }
 
diff --git a/test/Linker/Inputs/available_externally_over_decl.ll b/test/Linker/Inputs/available_externally_over_decl.ll
new file mode 100644
index 00000000000..b440fde9214
--- /dev/null
+++ b/test/Linker/Inputs/available_externally_over_decl.ll
@@ -0,0 +1,5 @@
+@h = global void ()* @f
+
+define available_externally void @f() {
+  ret void
+}
diff --git a/test/Linker/available_externally_over_decl.ll b/test/Linker/available_externally_over_decl.ll
new file mode 100644
index 00000000000..e220b17edf7
--- /dev/null
+++ b/test/Linker/available_externally_over_decl.ll
@@ -0,0 +1,9 @@
+; RUN: llvm-link -S %s %p/Inputs/available_externally_over_decl.ll | FileCheck %s
+
+declare void @f()
+
+define void ()* @main() {
+  ret void ()* @f
+}
+
+; CHECK: define available_externally void @f() {