diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -3750,38 +3750,49 @@
   Args.AddLastArg(CmdArgs, options::OPT_fmodules_prune_interval);
   Args.AddLastArg(CmdArgs, options::OPT_fmodules_prune_after);
 
-  Args.AddLastArg(CmdArgs, options::OPT_fbuild_session_timestamp);
+  if (HaveClangModules) {
+    Args.AddLastArg(CmdArgs, options::OPT_fbuild_session_timestamp);
 
-  if (Arg *A = Args.getLastArg(options::OPT_fbuild_session_file)) {
-    if (Args.hasArg(options::OPT_fbuild_session_timestamp))
-      D.Diag(diag::err_drv_argument_not_allowed_with)
-          << A->getAsString(Args) << "-fbuild-session-timestamp";
+    if (Arg *A = Args.getLastArg(options::OPT_fbuild_session_file)) {
+      if (Args.hasArg(options::OPT_fbuild_session_timestamp))
+        D.Diag(diag::err_drv_argument_not_allowed_with)
+            << A->getAsString(Args) << "-fbuild-session-timestamp";
 
-    llvm::sys::fs::file_status Status;
-    if (llvm::sys::fs::status(A->getValue(), Status))
-      D.Diag(diag::err_drv_no_such_file) << A->getValue();
-    CmdArgs.push_back(Args.MakeArgString(
-        "-fbuild-session-timestamp=" +
-        Twine((uint64_t)std::chrono::duration_cast<std::chrono::seconds>(
-                  Status.getLastModificationTime().time_since_epoch())
-                  .count())));
-  }
+      llvm::sys::fs::file_status Status;
+      if (llvm::sys::fs::status(A->getValue(), Status))
+        D.Diag(diag::err_drv_no_such_file) << A->getValue();
+      CmdArgs.push_back(Args.MakeArgString(
+          "-fbuild-session-timestamp=" +
+          Twine((uint64_t)std::chrono::duration_cast<std::chrono::seconds>(
+                    Status.getLastModificationTime().time_since_epoch())
+                    .count())));
+    }
 
-  if (Args.getLastArg(options::OPT_fmodules_validate_once_per_build_session)) {
-    if (!Args.getLastArg(options::OPT_fbuild_session_timestamp,
-                         options::OPT_fbuild_session_file))
-      D.Diag(diag::err_drv_modules_validate_once_requires_timestamp);
+    if (Args.getLastArg(
+            options::OPT_fmodules_validate_once_per_build_session)) {
+      if (!Args.getLastArg(options::OPT_fbuild_session_timestamp,
+                           options::OPT_fbuild_session_file))
+        D.Diag(diag::err_drv_modules_validate_once_requires_timestamp);
 
-    Args.AddLastArg(CmdArgs,
-                    options::OPT_fmodules_validate_once_per_build_session);
-  }
+      Args.AddLastArg(CmdArgs,
+                      options::OPT_fmodules_validate_once_per_build_session);
+    }
 
-  if (Args.hasFlag(options::OPT_fmodules_validate_system_headers,
-                   options::OPT_fno_modules_validate_system_headers,
-                   ImplicitModules))
-    CmdArgs.push_back("-fmodules-validate-system-headers");
+    if (Args.hasFlag(options::OPT_fmodules_validate_system_headers,
+                     options::OPT_fno_modules_validate_system_headers,
+                     ImplicitModules))
+      CmdArgs.push_back("-fmodules-validate-system-headers");
 
-  Args.AddLastArg(CmdArgs, options::OPT_fmodules_disable_diagnostic_validation);
+    Args.AddLastArg(CmdArgs,
+                    options::OPT_fmodules_disable_diagnostic_validation);
+  } else {
+    Args.ClaimAllArgs(options::OPT_fbuild_session_timestamp);
+    Args.ClaimAllArgs(options::OPT_fbuild_session_file);
+    Args.ClaimAllArgs(options::OPT_fmodules_validate_once_per_build_session);
+    Args.ClaimAllArgs(options::OPT_fmodules_validate_system_headers);
+    Args.ClaimAllArgs(options::OPT_fno_modules_validate_system_headers);
+    Args.ClaimAllArgs(options::OPT_fmodules_disable_diagnostic_validation);
+  }
 }
 
 static void RenderCharacterOptions(const ArgList &Args, const llvm::Triple &T,
diff --git a/clang/test/Driver/modules.m b/clang/test/Driver/modules.m
--- a/clang/test/Driver/modules.m
+++ b/clang/test/Driver/modules.m
@@ -4,27 +4,27 @@
 // RUN: %clang -fmodules -fno-modules -fmodules -### %s 2>&1 | FileCheck -check-prefix=CHECK-HAS-MODULES %s
 // CHECK-HAS-MODULES: -fmodules
 
-// RUN: %clang -fbuild-session-file=doesntexist -### %s 2>&1 | FileCheck -check-prefix=NOFILE %s
+// RUN: %clang -fmodules -fbuild-session-file=doesntexist -### %s 2>&1 | FileCheck -check-prefix=NOFILE %s
 // NOFILE: no such file or directory: 'doesntexist'
 
 // RUN: touch -m -a -t 201008011501 %t.build-session-file
-// RUN: %clang -fbuild-session-file=%t.build-session-file -### %s 2>&1 | FileCheck -check-prefix=TIMESTAMP_ONLY %s
+// RUN: %clang -fmodules -fbuild-session-file=%t.build-session-file -### %s 2>&1 | FileCheck -check-prefix=TIMESTAMP_ONLY %s
 
-// RUN: %clang -fbuild-session-timestamp=1280703457 -### %s 2>&1 | FileCheck -check-prefix=TIMESTAMP_ONLY %s
+// RUN: %clang -fmodules -fbuild-session-timestamp=1280703457 -### %s 2>&1 | FileCheck -check-prefix=TIMESTAMP_ONLY %s
 // TIMESTAMP_ONLY: -fbuild-session-timestamp=128{{([[:digit:]]{7})[^[:digit:]]}}
 
-// RUN: %clang -fbuild-session-file=%t.build-session-file -fbuild-session-timestamp=123 -### %s 2>&1 | FileCheck -check-prefix=CONFLICT %s
+// RUN: %clang -fmodules -fbuild-session-file=%t.build-session-file -fbuild-session-timestamp=123 -### %s 2>&1 | FileCheck -check-prefix=CONFLICT %s
 // CONFLICT: error: invalid argument '-fbuild-session-file={{.*}}.build-session-file' not allowed with '-fbuild-session-timestamp'
 
-// RUN: %clang -fbuild-session-timestamp=123 -fmodules-validate-once-per-build-session -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_ONCE %s
+// RUN: %clang -fmodules -fbuild-session-timestamp=123 -fmodules-validate-once-per-build-session -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_ONCE %s
 // MODULES_VALIDATE_ONCE: -fbuild-session-timestamp=123
 // MODULES_VALIDATE_ONCE: -fmodules-validate-once-per-build-session
 
-// RUN: %clang -fbuild-session-file=%t.build-session-file -fmodules-validate-once-per-build-session -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_ONCE_FILE %s
+// RUN: %clang -fmodules -fbuild-session-file=%t.build-session-file -fmodules-validate-once-per-build-session -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_ONCE_FILE %s
 // MODULES_VALIDATE_ONCE_FILE: -fbuild-session-timestamp=128{{([[:digit:]]{7})[^[:digit:]]}}
 // MODULES_VALIDATE_ONCE_FILE: -fmodules-validate-once-per-build-session
 
-// RUN: %clang -fmodules-validate-once-per-build-session -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_ONCE_ERR %s
+// RUN: %clang -fmodules -fmodules-validate-once-per-build-session -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_ONCE_ERR %s
 // MODULES_VALIDATE_ONCE_ERR: option '-fmodules-validate-once-per-build-session' requires '-fbuild-session-timestamp=<seconds since Epoch>' or '-fbuild-session-file=<file>'
 
 // RUN: %clang -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_SYSTEM_HEADERS_DEFAULT %s
@@ -33,16 +33,16 @@
 // RUN: %clang -fmodules -fsyntax-only -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_SYSTEM_HEADERS_DEFAULT_MOD %s
 // MODULES_VALIDATE_SYSTEM_HEADERS_DEFAULT_MOD: -fmodules-validate-system-headers
 
-// RUN: %clang -fmodules-validate-system-headers -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_SYSTEM_HEADERS %s
+// RUN: %clang -fmodules -fmodules-validate-system-headers -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_SYSTEM_HEADERS %s
 // MODULES_VALIDATE_SYSTEM_HEADERS: -fmodules-validate-system-headers
 
-// RUN: %clang -fno-modules-validate-system-headers -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_SYSTEM_HEADERS_NOSYSVALID %s
+// RUN: %clang -fmodules -fno-modules-validate-system-headers -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_SYSTEM_HEADERS_NOSYSVALID %s
 // MODULES_VALIDATE_SYSTEM_HEADERS_NOSYSVALID-NOT: -fmodules-validate-system-headers
 
 // RUN: %clang -### %s 2>&1 | FileCheck -check-prefix=MODULES_DISABLE_DIAGNOSTIC_VALIDATION_DEFAULT %s
 // MODULES_DISABLE_DIAGNOSTIC_VALIDATION_DEFAULT-NOT: -fmodules-disable-diagnostic-validation
 
-// RUN: %clang -fmodules-disable-diagnostic-validation -### %s 2>&1 | FileCheck -check-prefix=MODULES_DISABLE_DIAGNOSTIC_VALIDATION %s
+// RUN: %clang -fmodules -fmodules-disable-diagnostic-validation -### %s 2>&1 | FileCheck -check-prefix=MODULES_DISABLE_DIAGNOSTIC_VALIDATION %s
 // MODULES_DISABLE_DIAGNOSTIC_VALIDATION: -fmodules-disable-diagnostic-validation
 
 // RUN: %clang -fmodules -### %s 2>&1 | FileCheck -check-prefix=MODULES_PREBUILT_PATH_DEFAULT %s
@@ -70,3 +70,13 @@
 // CHECK-NO-MODULE-FILES-NOT: "-fmodules"
 // CHECK-NO-MODULE-FILES-NOT: "-fmodule-file=foo.pcm"
 // CHECK-NO-MODULE-FILES-NOT: "-fmodule-file=bar.pcm"
+
+// RUN: %clang -fno-modules -fbuild-session-file=%t.build-session-file -### %s 2>&1 | FileCheck -check-prefix=SESSION_FLAG %s
+// RUN: %clang -fno-modules -fbuild-session-timestamp=123 -### %s 2>&1 | FileCheck -check-prefix=SESSION_FLAG %s
+// SESSION_FLAG-NOT: -fbuild-session-timestamp
+
+// RUN: %clang -fno-modules -fmodules-validate-once-per-build-session -### %s 2>&1 | FileCheck -check-prefix=VALIDATE_ONCE_FLAG %s
+// VALIDATE_ONCE_FLAG-NOT: -fmodules-validate-once-per-build-session
+
+// RUN: %clang -fno-modules -fmodules-validate-system-headers -### %s 2>&1 | FileCheck -check-prefix=VALIDATE_SYSTEM_FLAG %s
+// VALIDATE_SYSTEM_FLAG-NOT: -fmodules-validate-system-headers