diff --git a/Basic/SourceManager.cpp b/Basic/SourceManager.cpp
index 4d525fc..96da763 100644
--- a/Basic/SourceManager.cpp
+++ b/Basic/SourceManager.cpp
@@ -234,7 +234,7 @@
 /// getSourceName - This method returns the name of the file or buffer that
 /// the SourceLocation specifies.  This can be modified with #line directives,
 /// etc.
-const char *SourceManager::getSourceName(SourceLocation Loc) {
+const char *SourceManager::getSourceName(SourceLocation Loc) const {
   unsigned FileID = Loc.getFileID();
   if (FileID == 0) return "";
   return getFileInfo(FileID)->Buffer->getBufferIdentifier();