1 files changed, 2 insertions, 1 deletions
diff --git a/src/chain.h b/src/chain.h
index 534f226f28..fc89599bd1 100644
--- a/src/chain.h
+++ b/src/chain.h
@@ -237,8 +237,9 @@ public:
         return ret;
     }
 
-    FlatFilePos GetUndoPos() const
+    FlatFilePos GetUndoPos() const EXCLUSIVE_LOCKS_REQUIRED(::cs_main)
     {
+        AssertLockHeld(::cs_main);
         FlatFilePos ret;
         if (nStatus & BLOCK_HAVE_UNDO) {
             ret.nFile = nFile;