diff --git a/src/runtime/initialize-component.ts b/src/runtime/initialize-component.ts
index 9a8da6d0700..47b3c1f1691 100644
--- a/src/runtime/initialize-component.ts
+++ b/src/runtime/initialize-component.ts
@@ -113,13 +113,38 @@ export const initializeComponent = async (
     }
 
     if (BUILD.style && Cstr && Cstr.style) {
-      // this component has styles but we haven't registered them yet
-      let style = Cstr.style;
-
-      if (BUILD.mode && typeof style !== 'string') {
+      /**
+       * this component has styles but we haven't registered them yet
+       */
+      let style: string | undefined;
+
+      if (typeof Cstr.style === 'string') {
+        /**
+         * in case the component has a `styleUrl` defined, e.g.
+         * ```ts
+         * @Component({
+         *   tag: 'my-component',
+         *   styleUrl: 'my-component.css'
+         * })
+         * ```
+         */
+        style = Cstr.style;
+      } else if (BUILD.mode && typeof Cstr.style !== 'string') {
+        /**
+         * in case the component has a `styleUrl` object defined, e.g.
+         * ```ts
+         * @Component({
+         *   tag: 'my-component',
+         *   styleUrl: {
+         *     ios: 'my-component.ios.css',
+         *     md: 'my-component.md.css'
+         *   }
+         * })
+         * ```
+         */
         hostRef.$modeName$ = computeMode(elm) as string | undefined;
         if (hostRef.$modeName$) {
-          style = style[hostRef.$modeName$];
+          style = Cstr.style[hostRef.$modeName$];
         }
 
         if (BUILD.hydrateServerSide && hostRef.$modeName$) {
diff --git a/src/runtime/styles.ts b/src/runtime/styles.ts
index ed600db3634..a060206b73b 100644
--- a/src/runtime/styles.ts
+++ b/src/runtime/styles.ts
@@ -47,7 +47,13 @@ export const registerStyle = (scopeId: string, cssText: string, allowCS: boolean
  * @param mode an optional current mode
  * @returns the scope ID for the component of interest
  */
-export const addStyle = (styleContainerNode: any, cmpMeta: d.ComponentRuntimeMeta, mode?: string) => {
+export const addStyle = (
+  styleContainerNode: Element | Document | ShadowRoot,
+  cmpMeta: d.ComponentRuntimeMeta,
+  mode?: string,
+) => {
+  const styleContainerDocument = styleContainerNode as Document;
+  const styleContainerShadowRoot = styleContainerNode as ShadowRoot;
   const scopeId = getScopeId(cmpMeta, mode);
   const style = styles.get(scopeId);
 
@@ -60,7 +66,7 @@ export const addStyle = (styleContainerNode: any, cmpMeta: d.ComponentRuntimeMet
 
   if (style) {
     if (typeof style === 'string') {
-      styleContainerNode = styleContainerNode.head || styleContainerNode;
+      styleContainerNode = styleContainerDocument.head || (styleContainerNode as HTMLElement);
       let appliedStyles = rootAppliedStyles.get(styleContainerNode);
       let styleElm;
       if (!appliedStyles) {
@@ -69,7 +75,7 @@ export const addStyle = (styleContainerNode: any, cmpMeta: d.ComponentRuntimeMet
       if (!appliedStyles.has(scopeId)) {
         if (
           BUILD.hydrateClientSide &&
-          styleContainerNode.host &&
+          styleContainerShadowRoot.host &&
           (styleElm = styleContainerNode.querySelector(`[${HYDRATED_STYLE_ID}="${scopeId}"]`))
         ) {
           // This is only happening on native shadow-dom, do not needs CSS var shim
@@ -100,8 +106,8 @@ export const addStyle = (styleContainerNode: any, cmpMeta: d.ComponentRuntimeMet
           appliedStyles.add(scopeId);
         }
       }
-    } else if (BUILD.constructableCSS && !styleContainerNode.adoptedStyleSheets.includes(style)) {
-      styleContainerNode.adoptedStyleSheets = [...styleContainerNode.adoptedStyleSheets, style];
+    } else if (BUILD.constructableCSS && !styleContainerDocument.adoptedStyleSheets.includes(style)) {
+      styleContainerDocument.adoptedStyleSheets = [...styleContainerDocument.adoptedStyleSheets, style];
     }
   }
   return scopeId;
@@ -119,7 +125,7 @@ export const attachStyles = (hostRef: d.HostRef) => {
   const flags = cmpMeta.$flags$;
   const endAttachStyles = createTime('attachStyles', cmpMeta.$tagName$);
   const scopeId = addStyle(
-    BUILD.shadowDom && supportsShadow && elm.shadowRoot ? elm.shadowRoot : elm.getRootNode(),
+    BUILD.shadowDom && supportsShadow && elm.shadowRoot ? elm.shadowRoot : (elm.getRootNode() as ShadowRoot),
     cmpMeta,
     hostRef.$modeName$,
   );