diff --git a/mlir/include/mlir/IR/Attributes.h b/mlir/include/mlir/IR/Attributes.h
--- a/mlir/include/mlir/IR/Attributes.h
+++ b/mlir/include/mlir/IR/Attributes.h
@@ -222,7 +222,7 @@
   class attr_value_iterator final
       : public llvm::mapped_iterator<iterator, AttrTy (*)(Attribute)> {
   public:
-    explicit attr_value_iterator(iterator it)
+    attr_value_iterator(iterator it) /* implicit */
         : llvm::mapped_iterator<iterator, AttrTy (*)(Attribute)>(
               it, [](Attribute attr) { return attr.cast<AttrTy>(); }) {}
     AttrTy operator*() { return (*this->I).template cast<AttrTy>(); }