diff --git a/clang/include/clang/Frontend/FrontendOptions.h b/clang/include/clang/Frontend/FrontendOptions.h
--- a/clang/include/clang/Frontend/FrontendOptions.h
+++ b/clang/include/clang/Frontend/FrontendOptions.h
@@ -16,9 +16,9 @@
 #include "clang/Serialization/ModuleFileExtension.h"
 #include "llvm/ADT/StringRef.h"
 #include <cassert>
+#include <map>
 #include <memory>
 #include <string>
-#include <unordered_map>
 #include <vector>
 
 namespace llvm {
@@ -404,7 +404,7 @@
   std::string ActionName;
 
   /// Args to pass to the plugins
-  std::unordered_map<std::string,std::vector<std::string>> PluginArgs;
+  std::map<std::string, std::vector<std::string>> PluginArgs;
 
   /// The list of plugin actions to run in addition to the normal action.
   std::vector<std::string> AddPluginActions;
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
@@ -877,4 +877,15 @@
             ShowIncludesDestination::Stdout);
   ASSERT_TRUE(Invocation.getDependencyOutputOpts().ShowHeaderIncludes);
 }
+
+TEST_F(CommandLineTest, PluginArgsRoundTripDeterminism) {
+  const char *Args[] = {
+      "-plugin-arg-blink-gc-plugin", "no-members-in-stack-allocated",
+      "-plugin-arg-find-bad-constructs", "checked-ptr-as-trivial-member",
+      "-plugin-arg-find-bad-constructs", "check-ipc",
+      // Enable round-trip to ensure '-plugin-arg' generation is deterministic.
+      "-round-trip-args"};
+
+  ASSERT_TRUE(CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags));
+}
 } // anonymous namespace