diff --git a/cmd/erasure-server-pool.go b/cmd/erasure-server-pool.go
index 002ef4cc9..f87cd4797 100644
--- a/cmd/erasure-server-pool.go
+++ b/cmd/erasure-server-pool.go
@@ -256,7 +256,7 @@ func (z *erasureServerPools) NewNSLock(bucket string, objects ...string) RWLocke
 
 // GetDisksID will return disks by their ID.
 func (z *erasureServerPools) GetDisksID(ids ...string) []StorageAPI {
-	idMap := make(map[string]struct{})
+	idMap := make(map[string]struct{}, len(ids))
 	for _, id := range ids {
 		idMap[id] = struct{}{}
 	}
diff --git a/cmd/signature-v4.go b/cmd/signature-v4.go
index f2386cc8e..ceb8b4b2f 100644
--- a/cmd/signature-v4.go
+++ b/cmd/signature-v4.go
@@ -60,7 +60,7 @@ const (
 // getCanonicalHeaders generate a list of request headers with their values
 func getCanonicalHeaders(signedHeaders http.Header) string {
 	var headers []string
-	vals := make(http.Header)
+	vals := make(http.Header, len(signedHeaders))
 	for k, vv := range signedHeaders {
 		k = strings.ToLower(k)
 		headers = append(headers, k)