diff --git a/packages/runtime/src/components/_internal/ImplWrapper/ImplWrapperMain.tsx b/packages/runtime/src/components/_internal/ImplWrapper/ImplWrapperMain.tsx
index 018f82cb..aeb28da4 100644
--- a/packages/runtime/src/components/_internal/ImplWrapper/ImplWrapperMain.tsx
+++ b/packages/runtime/src/components/_internal/ImplWrapper/ImplWrapperMain.tsx
@@ -68,9 +68,11 @@ export const ImplWrapperMain = React.forwardRef<HTMLDivElement, ImplWrapperProps
             return prevProps;
           }
 
-          return mergeWith(prevProps, result.props, (obj, src) => {
-            if (isArray(obj)) {
-              return obj.concat(src);
+          return mergeWith({}, prevProps, result.props, (target, src, key) => {
+            if (isArray(target)) {
+              return target.concat(src);
+            } else if (key === 'customStyle') {
+              return mergeCustomStyle(target, src);
             }
           });
         },
@@ -175,3 +177,14 @@ const useDidUpdate = (fn: Function) => {
     }
   });
 };
+
+function mergeCustomStyle(s1?: Record<string, string>, s2?: Record<string, string>) {
+  if (s1 && s2) {
+    return mergeWith({}, s1, s2, (target: string, src: string) => {
+      if (target && src) {
+        return `${target};${src}`;
+      }
+    });
+  }
+  return s1 || s2;
+}
diff --git a/packages/runtime/src/traits/core/Style.tsx b/packages/runtime/src/traits/core/Style.tsx
index 7cfbb148..3589c6b9 100644
--- a/packages/runtime/src/traits/core/Style.tsx
+++ b/packages/runtime/src/traits/core/Style.tsx
@@ -25,8 +25,12 @@ export default implementRuntimeTrait({
 })(() => {
   return ({ styles }) => {
     const customStyle: Record<string, string> = {};
-    styles.forEach(style => {
-      customStyle[style.styleSlot] = style.style;
+    styles.forEach(({ style, styleSlot }) => {
+      if (!customStyle[styleSlot]) {
+        customStyle[styleSlot] = '';
+      }
+      // add a ';' between css texts, in case user forgets to add ';' in the end
+      customStyle[styleSlot] = `${customStyle[styleSlot]};${style}`;
     });
     return {
       props: {