diff --git a/llvm/lib/Analysis/DataStructure/EquivClassGraphs.cpp b/llvm/lib/Analysis/DataStructure/EquivClassGraphs.cpp
index 2ddc684..e895ef3 100644
--- a/llvm/lib/Analysis/DataStructure/EquivClassGraphs.cpp
+++ b/llvm/lib/Analysis/DataStructure/EquivClassGraphs.cpp
@@ -106,7 +106,7 @@
   // Merge the globals variables (not the calls) from the globals graph back
   // into the main function's graph so that the main function contains all of
   // the information about global pools and GV usage in the program.
-  if (MainFunc) {
+  if (MainFunc && !MainFunc->isExternal()) {
     DSGraph &MainGraph = getOrCreateGraph(*MainFunc);
     const DSGraph &GG = *MainGraph.getGlobalsGraph();
     ReachabilityCloner RC(MainGraph, GG,