diff --git a/lib/Debugger/SourceFile.cpp b/lib/Debugger/SourceFile.cpp
index 799231fc8dd..ebea307be46 100644
--- a/lib/Debugger/SourceFile.cpp
+++ b/lib/Debugger/SourceFile.cpp
@@ -20,7 +20,7 @@ using namespace llvm;
 ///
 void SourceFile::readFile() {
   std::string ErrMsg;
-  if (File.map(&ErrMsg))
+  if (!File.map(&ErrMsg))
     throw ErrMsg;
 }