diff --git a/mlir/lib/IR/OperationSupport.cpp b/mlir/lib/IR/OperationSupport.cpp
--- a/mlir/lib/IR/OperationSupport.cpp
+++ b/mlir/lib/IR/OperationSupport.cpp
@@ -72,6 +72,7 @@
 }
 
 void NamedAttrList::push_back(NamedAttribute newAttribute) {
+  assert(newAttribute.second && "unexpected null attribute");
   if (isSorted())
     dictionarySorted.setInt(
         attrs.empty() ||