diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1683,7 +1683,6 @@
     // We can't find a module, error out here.
     getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_found)
         << ModuleName << SourceRange(ImportLoc, ModuleNameLoc);
-    DisableGeneratingGlobalModuleIndex = true;
     return nullptr;
   }
   if (ModuleFilename.empty()) {
@@ -1695,7 +1694,6 @@
 
     getDiagnostics().Report(ModuleNameLoc, diag::err_module_build_disabled)
         << ModuleName;
-    DisableGeneratingGlobalModuleIndex = true;
     return nullptr;
   }
 
@@ -1742,7 +1740,6 @@
         if (*ModuleFile == M->getASTFile())
           return M;
 
-    DisableGeneratingGlobalModuleIndex = true;
     getDiagnostics().Report(ModuleNameLoc, diag::err_module_prebuilt)
         << ModuleName;
     return ModuleLoadResult();
@@ -1764,14 +1761,12 @@
     LLVM_FALLTHROUGH;
   case ASTReader::VersionMismatch:
   case ASTReader::HadErrors:
-    // FIXME: Should this set DisableGeneratingGlobalModuleIndex = true?
     ModuleLoader::HadFatalFailure = true;
     // FIXME: The ASTReader will already have complained, but can we shoehorn
     // that diagnostic information into a more useful form?
     return ModuleLoadResult();
 
   case ASTReader::Failure:
-    // FIXME: Should this set DisableGeneratingGlobalModuleIndex = true?
     ModuleLoader::HadFatalFailure = true;
     return ModuleLoadResult();
   }
@@ -1781,7 +1776,6 @@
     // We don't know the desired configuration for this module and don't
     // necessarily even have a module map. Since ReadAST already produces
     // diagnostics for these two cases, we simply error out here.
-    DisableGeneratingGlobalModuleIndex = true;
     return ModuleLoadResult();
   }
 
@@ -1806,7 +1800,6 @@
 
     getDiagnostics().Report(ModuleNameLoc, diag::err_module_cycle)
         << ModuleName << CyclePath;
-    // FIXME: Should this set DisableGeneratingGlobalModuleIndex = true?
     return nullptr;
   }
 
@@ -1816,7 +1809,6 @@
       getPreprocessorOpts().FailedModules->hasAlreadyFailed(ModuleName)) {
     getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_built)
         << ModuleName << SourceRange(ImportLoc, ModuleNameLoc);
-    DisableGeneratingGlobalModuleIndex = true;
     return nullptr;
   }
 
@@ -1827,7 +1819,6 @@
            "undiagnosed error in compileModuleAndReadAST");
     if (getPreprocessorOpts().FailedModules)
       getPreprocessorOpts().FailedModules->addFailed(ModuleName);
-    DisableGeneratingGlobalModuleIndex = true;
     return nullptr;
   }
 
@@ -1878,11 +1869,10 @@
   } else {
     ModuleLoadResult Result = findOrCompileModuleAndReadAST(
         ModuleName, ImportLoc, ModuleNameLoc, IsInclusionDirective);
-    // FIXME: Can we pull 'DisableGeneratingGlobalModuleIndex = true' out of
-    // the return sequences for findOrCompileModuleAndReadAST and do it here
-    // (as long as the result is not a config mismatch)?  See FIXMEs there.
     if (!Result.isNormal())
       return Result;
+    if (!Result)
+      DisableGeneratingGlobalModuleIndex = true;
     Module = Result;
     MM.cacheModuleLoad(*Path[0].first, Module);
   }