diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index 0c885ff138f..5fba85cce4d 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -94,7 +94,7 @@ module ts {
             output += diagnostic.file.filename + "(" + loc.line + "," + loc.character + "): ";
         }
 
-        var category = DiagnosticCategory[diagnostic.category];
+        var category = DiagnosticCategory[diagnostic.category].toLowerCase();
         output += category + " TS" + diagnostic.code + ": " + diagnostic.messageText + sys.newLine;
 
         sys.write(output);