diff --git a/clang-tools-extra/modularize/ModularizeUtilities.cpp b/clang-tools-extra/modularize/ModularizeUtilities.cpp
index 3ef808d204c61..043f6f5b20b80 100644
--- a/clang-tools-extra/modularize/ModularizeUtilities.cpp
+++ b/clang-tools-extra/modularize/ModularizeUtilities.cpp
@@ -322,12 +322,13 @@ std::error_code ModularizeUtilities::loadModuleMap(
 // Walks the modules and collects referenced headers into
 // HeaderFileNames.
 bool ModularizeUtilities::collectModuleMapHeaders(clang::ModuleMap *ModMap) {
-  for (ModuleMap::module_iterator I = ModMap->module_begin(),
-    E = ModMap->module_end();
-    I != E; ++I) {
-    if (!collectModuleHeaders(*I->second))
+  SmallVector<std::pair<StringRef, const Module *>, 0> Vec;
+  for (auto &M : ModMap->modules())
+    Vec.emplace_back(M.first(), M.second);
+  llvm::sort(Vec, llvm::less_first());
+  for (auto &I : Vec)
+    if (!collectModuleHeaders(*I.second))
       return false;
-  }
   return true;
 }
 
diff --git a/clang-tools-extra/test/modularize/ProblemsDisplayLists.modularize b/clang-tools-extra/test/modularize/ProblemsDisplayLists.modularize
index afe1ece5eec08..9721561511263 100644
--- a/clang-tools-extra/test/modularize/ProblemsDisplayLists.modularize
+++ b/clang-tools-extra/test/modularize/ProblemsDisplayLists.modularize
@@ -12,5 +12,5 @@
 
 # CHECK: These are the combined files, with problem files preceded by #:
 
-# CHECK: Inputs/CompileError/Level1A.h
-# CHECK: {{.*}}Inputs/CompileError/HasError.h
+# CHECK:      Inputs/CompileError/HasError.h
+# CHECK-NEXT: Inputs/CompileError/Level1A.h