diff --git a/server/core/config_runtime.cc b/server/core/config_runtime.cc
index b83ede07b..b306f4d2f 100644
--- a/server/core/config_runtime.cc
+++ b/server/core/config_runtime.cc
@@ -1458,6 +1458,11 @@ bool runtime_alter_service_from_json(SERVICE* service, json_t* new_json)
                         rval = false;
                     }
                 }
+                else
+                {
+                    runtime_error("Parameter '%s' cannot be modified", key);
+                    rval = false;
+                }
             }
         }
     }