diff --git a/modules/module-lua-scripting/api/json.c b/modules/module-lua-scripting/api/json.c
index 242f0e41..5afa5c91 100644
--- a/modules/module-lua-scripting/api/json.c
+++ b/modules/module-lua-scripting/api/json.c
@@ -281,7 +281,7 @@ spa_json_array_new (lua_State *L)
           break;
         }
         default:
-          luaL_error (L, "Json does not support lua type ",
+          luaL_error (L, "Json does not support lua type %s",
               lua_typename(L, lua_type(L, -1)));
           break;
       }
@@ -327,7 +327,7 @@ spa_json_object_new (lua_State *L)
           break;
         }
         default:
-          luaL_error (L, "Json does not support lua type ",
+          luaL_error (L, "Json does not support lua type %s",
               lua_typename(L, lua_type(L, -1)));
           break;
       }