diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -4544,7 +4544,10 @@
         return CreateFromArgsImpl(Invocation, CommandLineArgs, Diags, Argv0);
       },
       [](CompilerInvocation &Invocation, SmallVectorImpl<const char *> &Args,
-         StringAllocator SA) { Invocation.generateCC1CommandLine(Args, SA); },
+         StringAllocator SA) {
+        Args.push_back("-cc1");
+        Invocation.generateCC1CommandLine(Args, SA);
+      },
       Invocation, DummyInvocation, CommandLineArgs, Diags, Argv0);
 }
 
diff --git a/clang/unittests/Frontend/CompilerInvocationTest.cpp b/clang/unittests/Frontend/CompilerInvocationTest.cpp
--- a/clang/unittests/Frontend/CompilerInvocationTest.cpp
+++ b/clang/unittests/Frontend/CompilerInvocationTest.cpp
@@ -145,6 +145,22 @@
   ASSERT_THAT(GeneratedArgs, Contains(StrEq("-fno-temp-file")));
 }
 
+TEST_F(CommandLineTest, CC1FlagPresentWhenDoingRoundTrip) {
+  const char *Args[] = {"-round-trip-args"};
+
+  ASSERT_TRUE(CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags));
+
+  ASSERT_THAT(GeneratedArgs, Contains(StrEq("-cc1")));
+}
+
+TEST_F(CommandLineTest, CC1FlagPresentWhenNotDoingRoundTrip) {
+  const char *Args[] = {"-no-round-trip-args", "-cc1"};
+
+  ASSERT_TRUE(CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags));
+
+  ASSERT_THAT(GeneratedArgs, Contains(StrEq("-cc1")));
+}
+
 TEST_F(CommandLineTest, BoolOptionDefaultTrueSingleFlagUnknownPresent) {
   const char *Args[] = {"-ftemp-file"};