diff --git a/src/hugr/rewrite/consts.rs b/src/hugr/rewrite/consts.rs
index f00b67cb04..9ebeff111a 100644
--- a/src/hugr/rewrite/consts.rs
+++ b/src/hugr/rewrite/consts.rs
@@ -32,6 +32,7 @@ pub enum RemoveConstIgnoreError {
     RemoveFail(#[from] HugrError),
 }
 
+#[rustversion::since(1.75)] // uses impl in return position
 impl Rewrite for RemoveConstIgnore {
     type Error = RemoveConstIgnoreError;
 
@@ -148,6 +149,7 @@ mod test {
         type_row,
         types::FunctionType,
     };
+    #[rustversion::since(1.75)] // uses impl in return position
     #[test]
     fn test_const_remove() -> Result<(), Box<dyn std::error::Error>> {
         let mut build = ModuleBuilder::new();