diff --git a/lib/Lex/PPDirectives.cpp b/lib/Lex/PPDirectives.cpp
index 8e76b92..5797b12 100644
--- a/lib/Lex/PPDirectives.cpp
+++ b/lib/Lex/PPDirectives.cpp
@@ -476,6 +476,9 @@
   // pp-directive.
   bool ReadAnyTokensBeforeDirective = CurPPLexer->MIOpt.getHasReadAnyTokensVal();
   
+  // Save the '#' token in case we need to return it later.
+  Token SavedHash = Result;
+  
   // Read the next token, the directive flavor.  This isn't expanded due to
   // C99 6.10.3p8.
   LexUnexpandedToken(Result);
@@ -568,6 +571,22 @@
     break;
   }
   
+  // If this is a .S file, treat unknown # directives as non-preprocessor
+  // directives.  This is important because # may be a comment or introduce
+  // various pseudo-ops.  Just return the # token and push back the following
+  // token to be lexed next time.
+  if (getLangOptions().AsmPreprocessor) {
+    Token *Toks = new Token[2]();
+    // Return the # and the token after it.
+    Toks[0] = SavedHash; 
+    Toks[1] = Result;
+    // Enter this token stream so that we re-lex the tokens.  Make sure to
+    // enable macro expansion, in case the token after the # is an identifier
+    // that is expanded.
+    EnterTokenStream(Toks, 2, false, true);
+    return;
+  }
+  
   // If we reached here, the preprocessing token is not valid!
   Diag(Result, diag::err_pp_invalid_directive);
   
diff --git a/lib/Lex/PPLexerChange.cpp b/lib/Lex/PPLexerChange.cpp
index 7c1a089..6f61c65 100644
--- a/lib/Lex/PPLexerChange.cpp
+++ b/lib/Lex/PPLexerChange.cpp
@@ -18,7 +18,6 @@
 #include "clang/Lex/LexDiagnostic.h"
 #include "clang/Basic/SourceManager.h"
 #include "llvm/Support/MemoryBuffer.h"
-
 using namespace clang;
 
 PPCallbacks::~PPCallbacks() {}