Index: test/Driver/unknown-arg.c
===================================================================
--- test/Driver/unknown-arg.c
+++ test/Driver/unknown-arg.c
@@ -14,6 +14,8 @@
 // RUN: FileCheck %s --check-prefix=SILENT
 // RUN: not %clang -cc1as -hell --version -debug-info-macros 2>&1 | \
 // RUN: FileCheck %s --check-prefix=CC1AS-DID-YOU-MEAN
+// RUN: not %clang -cc1asphalt -help 2>&1 | \
+// RUN: FileCheck %s --check-prefix=UNKNOWN-INTEGRATED
 
 // CHECK: error: unknown argument: '-cake-is-lie'
 // CHECK: error: unknown argument: '-%0'
@@ -46,7 +48,7 @@
 // CC1AS-DID-YOU-MEAN: error: unknown argument '-hell', did you mean '-help'?
 // CC1AS-DID-YOU-MEAN: error: unknown argument '--version', did you mean '-version'?
 // CC1AS-DID-YOU-MEAN: error: unknown argument '-debug-info-macros', did you mean '-debug-info-macro'?
-
+// UNKNOWN-INTEGRATED: error: unknown integrated tool 'asphalt'. Valid tools include '-cc1' and '-cc1as'.
 
 // RUN: %clang -S %s -o %t.s  -Wunknown-to-clang-option 2>&1 | FileCheck --check-prefix=IGNORED %s
 
Index: tools/driver/driver.cpp
===================================================================
--- tools/driver/driver.cpp
+++ tools/driver/driver.cpp
@@ -311,7 +311,8 @@
     return cc1as_main(argv.slice(2), argv[0], GetExecutablePathVP);
 
   // Reject unknown tools.
-  llvm::errs() << "error: unknown integrated tool '" << Tool << "'\n";
+  llvm::errs() << "error: unknown integrated tool '" << Tool << "'. "
+               << "Valid tools include '-cc1' and '-cc1as'.\n";
   return 1;
 }