diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs
index 50a00714ea06c..ef40c0706b4e2 100644
--- a/src/libstd/collections/hash/map.rs
+++ b/src/libstd/collections/hash/map.rs
@@ -966,7 +966,7 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
     pub fn clear(&mut self) {
         // Prevent reallocations from happening from now on. Makes it possible
         // for the map to be reused but has a downside: reserves permanently.
-        self.resize_policy.reserve(self.table.size());
+        self.resize_policy.reserve(max(self.table.size(), INITIAL_CAPACITY).next_power_of_two());
 
         let cap = self.table.capacity();
         let mut buckets = Bucket::first(&mut self.table);