Index: cfe/trunk/lib/Frontend/CompilerInstance.cpp
===================================================================
--- cfe/trunk/lib/Frontend/CompilerInstance.cpp
+++ cfe/trunk/lib/Frontend/CompilerInstance.cpp
@@ -1727,7 +1727,9 @@
     // module cache, we don't know how to rebuild modules.
     unsigned ARRFlags = Source == ModuleCache ?
                         ASTReader::ARR_OutOfDate | ASTReader::ARR_Missing :
-                        ASTReader::ARR_ConfigurationMismatch;
+                        Source == PrebuiltModulePath ?
+                            0 :
+                            ASTReader::ARR_ConfigurationMismatch;
     switch (ModuleManager->ReadAST(ModuleFileName,
                                    Source == PrebuiltModulePath
                                        ? serialization::MK_PrebuiltModule
Index: cfe/trunk/test/Modules/mismatch-diagnostics.cpp
===================================================================
--- cfe/trunk/test/Modules/mismatch-diagnostics.cpp
+++ cfe/trunk/test/Modules/mismatch-diagnostics.cpp
@@ -0,0 +1,22 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t/prebuilt_modules
+//
+// RUN: %clang_cc1 -triple %itanium_abi_triple                          \
+// RUN:     -fmodules-ts -fprebuilt-module-path=%t/prebuilt-modules     \
+// RUN:     -emit-module-interface -pthread -DBUILD_MODULE              \
+// RUN:     %s -o %t/prebuilt_modules/mismatching_module.pcm
+//
+// RUN: not %clang_cc1 -triple %itanium_abi_triple -fmodules-ts         \
+// RUN:     -fprebuilt-module-path=%t/prebuilt_modules -DCHECK_MISMATCH \
+// RUN:     %s 2>&1 | FileCheck %s
+
+#ifdef BUILD_MODULE
+export module mismatching_module;
+#endif
+
+#ifdef CHECK_MISMATCH
+import mismatching_module;
+// CHECK: error: POSIX thread support was enabled in PCH file but is currently disabled
+// CHECK-NEXT: module file {{.*}}/mismatching_module.pcm cannot be loaded due to a configuration mismatch with the current compilation
+#endif
+