diff --git a/libcxx/include/__iterator/wrap_iter.h b/libcxx/include/__iterator/wrap_iter.h
--- a/libcxx/include/__iterator/wrap_iter.h
+++ b/libcxx/include/__iterator/wrap_iter.h
@@ -136,13 +136,15 @@
 
 private:
 #if _LIBCPP_DEBUG_LEVEL == 2
-    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11 __wrap_iter(const void* __p, iterator_type __x) : __i(__x)
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit __wrap_iter(const void* __p, iterator_type __x) : __i(__x)
     {
       if (!__libcpp_is_constant_evaluated())
         __get_db()->__insert_ic(this, __p);
     }
 #else
-    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11 __wrap_iter(iterator_type __x) _NOEXCEPT : __i(__x) {}
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit __wrap_iter(iterator_type __x) _NOEXCEPT : __i(__x) {}
 #endif
 
     template <class _Up> friend class __wrap_iter;