diff --git a/packages/editor-ui/src/components/ParameterInputFull.vue b/packages/editor-ui/src/components/ParameterInputFull.vue
index ef994e507d..0861eef123 100644
--- a/packages/editor-ui/src/components/ParameterInputFull.vue
+++ b/packages/editor-ui/src/components/ParameterInputFull.vue
@@ -255,6 +255,8 @@ export default mixins(showMessage).extend({
 						prevValue.length > 1
 					) {
 						updatedValue = `${prevValue} ${data}`;
+					} else if (prevValue && ['string', 'json'].includes(this.parameter.type)) {
+						updatedValue = `=${prevValue} ${data}`;
 					} else {
 						updatedValue = `=${data}`;
 					}