diff --git a/pkgs/development/interpreters/ruby/bundler-env/default-gem-config.nix b/pkgs/development/interpreters/ruby/bundler-env/default-gem-config.nix
index cadda288764..b7ddfdea80b 100644
--- a/pkgs/development/interpreters/ruby/bundler-env/default-gem-config.nix
+++ b/pkgs/development/interpreters/ruby/bundler-env/default-gem-config.nix
@@ -31,7 +31,7 @@ in
 
 {
   charlock_holmes = attrs: {
-    buildInputs = [ which icu ];
+    buildInputs = [ which icu zlib ];
   };
 
   ffi = attrs: {