diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index 2f5ff604df3..57ad0260cb6 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -68,7 +68,7 @@ var sys: System = (function () {
                 return fileStream.ReadText();
             }
             catch (e) {
-                throw e.number === -2147024809 ? new Error(ts.Diagnostics.Unsupported_file_encoding.key) : e;
+                throw e;
             }
             finally {
                 fileStream.Close();
diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index c8cccd2da1c..52dac9695de 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -142,14 +142,19 @@ module ts {
             // otherwise use toLowerCase as a canonical form.
             return sys.useCaseSensitiveFileNames ? fileName : fileName.toLowerCase();
         }
-
+        
+        // returned by CScript sys environment
+        var unsupportedFileEncodingErrorCode = -2147024809;
+        
         function getSourceFile(filename: string, languageVersion: ScriptTarget, onError?: (message: string) => void): SourceFile {
             try {
                 var text = sys.readFile(filename, options.charset);
             }
             catch (e) {
                 if (onError) {
-                    onError(e.message);
+                    onError(e.number === unsupportedFileEncodingErrorCode ? 
+                                getDiagnosticText(Diagnostics.Unsupported_file_encoding) :
+                                e.message);
                 }
                 text = "";
             }