diff --git a/clippy_lints/src/methods/map_unwrap_or.rs b/clippy_lints/src/methods/map_unwrap_or.rs
index 7a19ac42e5ed..c90fba815e71 100644
--- a/clippy_lints/src/methods/map_unwrap_or.rs
+++ b/clippy_lints/src/methods/map_unwrap_or.rs
@@ -61,6 +61,7 @@ pub(super) fn lint<'a, 'tcx>(
                 arg, suggest
             )
         } else {
+            debug_assert!(is_result);
             "called `map(f).unwrap_or(a)` on a Result value. \
              This can be done more directly by calling `map_or(a, f)` instead"
                 .to_string()