diff --git a/lib/Analysis/DataStructure/DataStructure.cpp b/lib/Analysis/DataStructure/DataStructure.cpp
index c25c8d2..fbd223f 100644
--- a/lib/Analysis/DataStructure/DataStructure.cpp
+++ b/lib/Analysis/DataStructure/DataStructure.cpp
@@ -826,8 +826,8 @@
 /// merges the nodes specified in the call site with the formal arguments in the
 /// graph.
 ///
-void DSGraph::mergeInGraph(DSCallSite &CS, Function &F, const DSGraph &Graph,
-                           unsigned CloneFlags) {
+void DSGraph::mergeInGraph(const DSCallSite &CS, Function &F,
+                           const DSGraph &Graph, unsigned CloneFlags) {
   ScalarMapTy OldValMap, *ScalarMap;
   DSNodeHandle RetVal;