diff --git a/packages/runtime-core/__tests__/apiWatch.spec.ts b/packages/runtime-core/__tests__/apiWatch.spec.ts
index 07a589fb0f5..484fed4745c 100644
--- a/packages/runtime-core/__tests__/apiWatch.spec.ts
+++ b/packages/runtime-core/__tests__/apiWatch.spec.ts
@@ -1446,6 +1446,33 @@ describe('api: watch', () => {
     expect(spy).toHaveBeenCalledTimes(2)
   })
 
+  test('watching keypath should not stop on falsy intermediate values', async () => {
+    const spy = vi.fn()
+    const Comp = defineComponent({
+      render() {},
+      data() {
+        return {
+          a: {
+            b: 0 as any,
+          },
+        }
+      },
+      created(this: any) {
+        this.$watch('a.b', spy)
+      },
+      mounted(this: any) {
+        this.a.b = 1
+      },
+    })
+
+    const root = nodeOps.createElement('div')
+    createApp(Comp).mount(root)
+
+    await nextTick()
+    expect(spy).toHaveBeenCalledTimes(1)
+    expect(spy).toHaveBeenCalledWith(1, 0, expect.anything())
+  })
+
   it('watching sources: ref<any[]>', async () => {
     const foo = ref([1])
     const spy = vi.fn()
diff --git a/packages/runtime-core/src/apiWatch.ts b/packages/runtime-core/src/apiWatch.ts
index 4540ba1b03a..e6d0a3795df 100644
--- a/packages/runtime-core/src/apiWatch.ts
+++ b/packages/runtime-core/src/apiWatch.ts
@@ -274,7 +274,7 @@ export function createPathGetter(
   const segments = path.split('.')
   return (): WatchSource | WatchSource[] | WatchEffect | object => {
     let cur = ctx
-    for (let i = 0; i < segments.length && cur; i++) {
+    for (let i = 0; i < segments.length && cur != null; i++) {
       cur = cur[segments[i] as keyof typeof cur]
     }
     return cur
diff --git a/packages/runtime-dom/__tests__/patchStyle.spec.ts b/packages/runtime-dom/__tests__/patchStyle.spec.ts
index 8b2765e2149..56960751e1a 100644
--- a/packages/runtime-dom/__tests__/patchStyle.spec.ts
+++ b/packages/runtime-dom/__tests__/patchStyle.spec.ts
@@ -167,4 +167,15 @@ describe(`runtime-dom: style patching`, () => {
     patchProp(el, 'style', 'color:red', { fontSize: '12px' })
     expect(el.style.cssText.replace(/\s/g, '')).toBe('font-size:12px;')
   })
+
+  it('should handle string style with trailing semicolon when patching to object', () => {
+    const el = document.createElement('div')
+    // set initial string style with trailing semicolon
+    patchProp(el, 'style', {}, 'color:red;')
+    expect(el.style.cssText.replace(/\s/g, '')).toBe('color:red;')
+
+    // patch from string to object, entries without colon (from trailing ;) should be skipped
+    patchProp(el, 'style', 'color:red;', { fontSize: '12px' })
+    expect(el.style.cssText.replace(/\s/g, '')).toBe('font-size:12px;')
+  })
 })
diff --git a/packages/runtime-dom/src/modules/style.ts b/packages/runtime-dom/src/modules/style.ts
index 679064bd709..48ab9d6e3cb 100644
--- a/packages/runtime-dom/src/modules/style.ts
+++ b/packages/runtime-dom/src/modules/style.ts
@@ -25,7 +25,9 @@ export function patchStyle(el: Element, prev: Style, next: Style): void {
         }
       } else {
         for (const prevStyle of prev.split(';')) {
-          const key = prevStyle.slice(0, prevStyle.indexOf(':')).trim()
+          const colonIndex = prevStyle.indexOf(':')
+          if (colonIndex < 0) continue
+          const key = prevStyle.slice(0, colonIndex).trim()
           if (next[key] == null) {
             setStyle(style, key, '')
           }