diff --git a/src/modules/custom/custom.c b/src/modules/custom/custom.c
index b31c6a0d..20055601 100644
--- a/src/modules/custom/custom.c
+++ b/src/modules/custom/custom.c
@@ -57,8 +57,8 @@ void ffInitCustomOptions(FFCustomOptions* options)
         NULL,
         ffGenerateCustomJsonConfig
     );
-    ffOptionInitModuleArg(&options->moduleArgs, "");
-    ffStrbufSetStatic(&options->moduleArgs.key, "");
+    ffOptionInitModuleArg(&options->moduleArgs, "");
+    ffStrbufSetStatic(&options->moduleArgs.key, " ");
 }
 
 void ffDestroyCustomOptions(FFCustomOptions* options)