diff --git a/Driver/RewriteObjC.cpp b/Driver/RewriteObjC.cpp
index 804a891..a3ce8a8 100644
--- a/Driver/RewriteObjC.cpp
+++ b/Driver/RewriteObjC.cpp
@@ -1572,9 +1572,21 @@
 void RewriteObjC::RewriteObjCQualifiedInterfaceTypes(Expr *E) {
   QualType Type = E->getType();
   if (needToScanForQualifiers(Type)) {
-    SourceLocation Loc = E->getLocStart();
+    SourceLocation Loc, EndLoc;
+    
+    if (const CStyleCastExpr *ECE = dyn_cast<CStyleCastExpr>(E)) {
+      Loc = ECE->getLParenLoc();
+      EndLoc = ECE->getRParenLoc();
+    } else {
+      Loc = E->getLocStart();
+      EndLoc = E->getLocEnd();
+    }
+    // This will defend against trying to rewrite synthesized expressions.
+    if (Loc.isInvalid() || EndLoc.isInvalid())
+      return;
+
     const char *startBuf = SM->getCharacterData(Loc);
-    const char *endBuf = SM->getCharacterData(E->getLocEnd());
+    const char *endBuf = SM->getCharacterData(EndLoc);
     const char *startRef = 0, *endRef = 0;
     if (scanForProtocolRefs(startBuf, endBuf, startRef, endRef)) {
       // Get the locations of the startRef, endRef.
diff --git a/test/Rewriter/crash.m b/test/Rewriter/crash.m
index 59f18f3..2e34850 100644
--- a/test/Rewriter/crash.m
+++ b/test/Rewriter/crash.m
@@ -12,3 +12,14 @@
     return 0;
 }
 
+// rdar://6291588
+@protocol A
+@end
+
+@interface Foo
+@end
+
+void func() {
+  id <A> obj = (id <A>)[Foo bar];
+}
+