diff --git a/src/mongo/util/functional.h b/src/mongo/util/functional.h
index c30089a64e9fe..1673382fa9fcc 100644
--- a/src/mongo/util/functional.h
+++ b/src/mongo/util/functional.h
@@ -123,6 +123,8 @@ class unique_function<RetType(Args...)> {
     // NOTE: This is not quite able to disable all `std::function` conversions on MSVC, at this
     // time.
     template <typename Signature>
+    operator std::function<Signature>() = delete;
+    template <typename Signature>
     operator std::function<Signature>() const = delete;
 
 private: