diff --git a/clang/lib/Serialization/ModuleManager.cpp b/clang/lib/Serialization/ModuleManager.cpp
--- a/clang/lib/Serialization/ModuleManager.cpp
+++ b/clang/lib/Serialization/ModuleManager.cpp
@@ -232,9 +232,15 @@
   // Read the signature eagerly now so that we can check it.  Avoid calling
   // ReadSignature unless there's something to check though.
   if (ExpectedSignature && checkSignature(ReadSignature(NewModule->Data),
-                                          ExpectedSignature, ErrorStr))
+                                          ExpectedSignature, ErrorStr)) {
+    // Try to remove the buffer.  If it can't be removed, then it was already
+    // validated by this process.
+    if (!getModuleCache().tryToDropPCM(NewModule->FileName)) {
+      const FileEntry *FE = NewModule->File;
+      FileMgr.invalidateCache(const_cast<FileEntry *>(FE));
+    }
     return OutOfDate;
-
+  }
   // We're keeping this module.  Store it everywhere.
   Module = Modules[Entry] = NewModule.get();
 
@@ -284,6 +290,8 @@
   for (ModuleIterator victim = First; victim != Last; ++victim) {
     Modules.erase(victim->File);
 
+    const FileEntry *FE = victim->File;
+    FileMgr.invalidateCache(const_cast<FileEntry *>(FE));
     if (modMap) {
       StringRef ModuleName = victim->ModuleName;
       if (Module *mod = modMap->findModule(ModuleName)) {