diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
index bb59400de47..9c3f1834801 100644
--- a/lib/Linker/LinkModules.cpp
+++ b/lib/Linker/LinkModules.cpp
@@ -1533,8 +1533,7 @@ bool ModuleLinker::run() {
     LazilyLinkGlobalValues.pop_back();
 
     if (auto F = dyn_cast<Function>(SGV))
-      if (F->isDeclaration())
-        continue;
+      assert(!F->isDeclaration() && "users should not pass down decls");
     if (linkGlobalValueBody(*SGV))
       return true;
   }