diff --git a/src/hash.ml b/src/hash.ml
index 36be50ee..84ceda9d 100644
--- a/src/hash.ml
+++ b/src/hash.ml
@@ -89,17 +89,13 @@ module Cstring = struct
   module H32 = struct
     include H32
 
-    let hash s =
-      let s = s ^ "\x00" in
-      hash s
+    let hash s = hash (s ^ "\x00")
   end
 
   module H64 = struct
     include H64
 
-    let hash s =
-      let s = s ^ "\x00" in
-      hash s
+    let hash s = hash (s ^ "\x00")
   end
 end