Index: cfe/trunk/test/Driver/unknown-arg.c
===================================================================
--- cfe/trunk/test/Driver/unknown-arg.c
+++ cfe/trunk/test/Driver/unknown-arg.c
@@ -12,6 +12,8 @@
 // RUN: FileCheck %s --check-prefix=CL-ERROR-DID-YOU-MEAN
 // RUN: %clang_cl -cake-is-lie -%0 -%d -HHHH -munknown-to-clang-option -print-stats -funknown-to-clang-option -c -Wno-unknown-argument -### -- %s 2>&1 | \
 // 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
 
 // CHECK: error: unknown argument: '-cake-is-lie'
 // CHECK: error: unknown argument: '-%0'
@@ -41,6 +43,9 @@
 // CL-ERROR-DID-YOU-MEAN: error: unknown argument ignored in clang-cl '-helo' (did you mean '-help'?)
 // SILENT-NOT: error:
 // SILENT-NOT: warning:
+// 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'?
 
 
 // RUN: %clang -S %s -o %t.s  -Wunknown-to-clang-option 2>&1 | FileCheck --check-prefix=IGNORED %s
Index: cfe/trunk/tools/driver/cc1as_main.cpp
===================================================================
--- cfe/trunk/tools/driver/cc1as_main.cpp
+++ cfe/trunk/tools/driver/cc1as_main.cpp
@@ -181,7 +181,13 @@
 
   // Issue errors on unknown arguments.
   for (const Arg *A : Args.filtered(OPT_UNKNOWN)) {
-    Diags.Report(diag::err_drv_unknown_argument) << A->getAsString(Args);
+    auto ArgString = A->getAsString(Args);
+    std::string Nearest;
+    if (OptTbl->findNearest(ArgString, Nearest, IncludedFlagsBitmask) > 1)
+      Diags.Report(diag::err_drv_unknown_argument) << ArgString;
+    else
+      Diags.Report(diag::err_drv_unknown_argument_with_suggestion)
+          << ArgString << Nearest;
     Success = false;
   }