diff --git a/lib/Analysis/BugReporter.cpp b/lib/Analysis/BugReporter.cpp
index 13b7f45..2a9531d 100644
--- a/lib/Analysis/BugReporter.cpp
+++ b/lib/Analysis/BugReporter.cpp
@@ -1818,8 +1818,23 @@
   R->getRanges(Beg, End);
   Diagnostic& Diag = getDiagnostic();
   FullSourceLoc L(R->getLocation(), getSourceManager());
-  unsigned ErrorDiag = Diag.getCustomDiagID(Diagnostic::Warning,
-                                            R->getShortDescription());
+  
+  // Search the description for '%', as that will be interpretted as a
+  // format character by FormatDiagnostics.
+  llvm::StringRef desc = R->getShortDescription();
+  unsigned ErrorDiag;
+  {
+    llvm::SmallString<512> TmpStr;
+    llvm::raw_svector_ostream Out(TmpStr);
+    for (llvm::StringRef::iterator I=desc.begin(), E=desc.end(); I!=E; ++I)
+      if (*I == '%')
+        Out << "%%";
+      else
+        Out << *I;
+    
+    Out.flush();
+    ErrorDiag = Diag.getCustomDiagID(Diagnostic::Warning, TmpStr);
+  }        
 
   switch (End-Beg) {
     default: assert(0 && "Don't handle this many ranges yet!");
diff --git a/test/Analysis/misc-ps.m b/test/Analysis/misc-ps.m
index 149be03..9543a98 100644
--- a/test/Analysis/misc-ps.m
+++ b/test/Analysis/misc-ps.m
@@ -801,3 +801,13 @@
   [p testBadArg:y]; // expected-warning{{Pass-by-value argument in message expression is undefined}}
 }
 
+//===----------------------------------------------------------------------===//
+// PR 6033 - Test emitting the correct output in a warning where we use '%'
+//  with operands that are undefined.
+//===----------------------------------------------------------------------===//
+
+int pr6033(int x) {
+  int y;
+  return x % y; // expected-warning{{The right operand of '%' is a garbage value}}
+}
+