diff --git a/lib/AST/DeclCXX.cpp b/lib/AST/DeclCXX.cpp
index 979723a..5064ec5 100644
--- a/lib/AST/DeclCXX.cpp
+++ b/lib/AST/DeclCXX.cpp
@@ -589,6 +589,8 @@
 static OverriddenMethodsMapTy *OverriddenMethods = 0;
 
 void CXXMethodDecl::addOverriddenMethod(const CXXMethodDecl *MD) {
+  assert(MD->isCanonicalDecl() && "Method is not canonical!");
+  
   // FIXME: The CXXMethodDecl dtor needs to remove and free the entry.
 
   if (!OverriddenMethods)