diff --git a/lib/Core/ExecutionState.h b/lib/Core/ExecutionState.h
index be63b654bc..a40c6a0982 100644
--- a/lib/Core/ExecutionState.h
+++ b/lib/Core/ExecutionState.h
@@ -230,7 +230,6 @@ struct MemorySubobject {
   unsigned size;
   explicit MemorySubobject(ref<Expr> address, unsigned size)
       : address(address), size(size) {}
-  MemorySubobject &operator=(const MemorySubobject &other) = default;
 };
 
 struct MemorySubobjectHash {