diff --git a/src/cargo/core/resolver/dep_cache.rs b/src/cargo/core/resolver/dep_cache.rs
index 79e44f6eba2..dd86170035e 100644
--- a/src/cargo/core/resolver/dep_cache.rs
+++ b/src/cargo/core/resolver/dep_cache.rs
@@ -109,7 +109,7 @@ impl<'a> RegistryQueryer<'a> {
             self.registry_cache.insert(dep.clone(), Poll::Pending);
             return Poll::Pending;
         }
-        for summary in ret.iter_mut() {
+        for summary in ret.iter() {
             let mut potential_matches = self
                 .replacements
                 .iter()