diff --git a/crates/ra_hir_ty/src/infer.rs b/crates/ra_hir_ty/src/infer.rs
index 98baeed6f6..bbbc391c4f 100644
--- a/crates/ra_hir_ty/src/infer.rs
+++ b/crates/ra_hir_ty/src/infer.rs
@@ -375,11 +375,9 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         match assoc_ty {
             Some(res_assoc_ty) => {
                 let ty = self.table.new_type_var();
-                let mut builder = Substs::build_for_def(self.db, res_assoc_ty).push(inner_ty);
-                for ty in params {
-                    builder = builder.push(ty.clone());
-                }
-
+                let builder = Substs::build_for_def(self.db, res_assoc_ty)
+                    .push(inner_ty)
+                    .fill(params.iter().cloned());
                 let projection = ProjectionPredicate {
                     ty: ty.clone(),
                     projection_ty: ProjectionTy {