diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
index c849b5417b6901fb0d31934b550ff78acb84d053..bc588ac4542b26fe06f97becb14943f287c608bb 100644
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -189,10 +189,13 @@ public:
 
   using Decl::isModulePrivate;
   using Decl::setModulePrivate;
-  
+
   /// \brief Determine whether this declaration is hidden from name lookup.
   bool isHidden() const { return Hidden; }
-  
+
+  /// \brief Set whether this declaration is hidden from name lookup.
+  void setHidden(bool Hide) { Hidden = Hide; }
+
   /// \brief Determine whether this declaration is a C++ class member.
   bool isCXXClassMember() const {
     const DeclContext *DC = getDeclContext();
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index a6b6e36bb7d2e9e7c43f0d54b7446147cf829fa3..39c4211892229823fcafd3fbed7e059c87c3aaeb 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -1949,8 +1949,12 @@ void Sema::DeclareGlobalAllocationFunction(DeclarationName Name,
             Func->getParamDecl(0)->getType().getUnqualifiedType());
         // FIXME: Do we need to check for default arguments here?
         if (Func->getNumParams() == 1 && InitialParamType == Argument) {
-          if(AddMallocAttr && !Func->hasAttr<MallocAttr>())
+          if (AddMallocAttr && !Func->hasAttr<MallocAttr>())
             Func->addAttr(::new (Context) MallocAttr(SourceLocation(), Context));
+          // Make the function visible to name lookup, even if we found it in an
+          // unimported module. It either is an implicitly-declared global
+          // allocation function, or is suppressing that function.
+          Func->setHidden(false);
           return;
         }
       }
diff --git a/clang/test/Modules/Inputs/cxx-decls-imported.h b/clang/test/Modules/Inputs/cxx-decls-imported.h
new file mode 100644
index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
diff --git a/clang/test/Modules/Inputs/cxx-decls-unimported.h b/clang/test/Modules/Inputs/cxx-decls-unimported.h
new file mode 100644
index 0000000000000000000000000000000000000000..0431e324616e52d1513981a1e3b92cbc926abbe5
--- /dev/null
+++ b/clang/test/Modules/Inputs/cxx-decls-unimported.h
@@ -0,0 +1 @@
+void operator delete(void*);
diff --git a/clang/test/Modules/Inputs/module.map b/clang/test/Modules/Inputs/module.map
index a4ac5b14de34d1424ae284d83b7574bc7bdeaed8..0a84f88b0af8e1a978747c3dddf6408468de1d7e 100644
--- a/clang/test/Modules/Inputs/module.map
+++ b/clang/test/Modules/Inputs/module.map
@@ -200,6 +200,15 @@ module cxx_templates_b {
   header "cxx-templates-b.h"
 }
 
+module cxx_decls {
+  module unimported {
+    header "cxx-decls-unimported.h"
+  }
+  module imported {
+    header "cxx-decls-imported.h"
+  }
+}
+
 module config {
   header "config.h"
   config_macros [exhaustive] WANT_FOO, WANT_BAR
diff --git a/clang/test/Modules/cxx-decls.cpp b/clang/test/Modules/cxx-decls.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..733e3f90bc76e3cb237cf6bcbc1bd77b463fba13
--- /dev/null
+++ b/clang/test/Modules/cxx-decls.cpp
@@ -0,0 +1,12 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -x objective-c++ -fmodules -fmodules-cache-path=%t -I %S/Inputs %s -verify -std=c++11
+
+// expected-no-diagnostics
+
+@import cxx_decls.imported;
+
+void test_delete(int *p) {
+  // We can call the normal global deallocation function even though it has only
+  // ever been explicitly declared in an unimported submodule.
+  delete p;
+}