diff --git a/src/node/server/serverPluginHmr.ts b/src/node/server/serverPluginHmr.ts
index 81936a6650d614..b0050ada1b7f49 100644
--- a/src/node/server/serverPluginHmr.ts
+++ b/src/node/server/serverPluginHmr.ts
@@ -150,47 +150,43 @@ export const hmrPlugin: ServerPlugin = ({
     }
 
     const publicPath = resolver.fileToRequest(filePath)
-    const importers = importerMap.get(publicPath)
-    if (importers) {
-      const hmrBoundaries = new Set<string>()
-      const dirtyFiles = new Set<string>()
-      dirtyFiles.add(publicPath)
-
-      const hasDeadEnd = walkImportChain(
-        publicPath,
-        importers,
-        hmrBoundaries,
-        dirtyFiles
-      )
-
-      // record dirty files - this is used when HMR requests coming in with
-      // timestamp to determine what files need to be force re-fetched
-      hmrDirtyFilesMap.set(String(timestamp), dirtyFiles)
+    const importers = ensureMapEntry(importerMap, publicPath)
+    const hmrBoundaries = new Set<string>()
+    const dirtyFiles = new Set<string>()
+    dirtyFiles.add(publicPath)
+
+    const hasDeadEnd = walkImportChain(
+      publicPath,
+      importers,
+      hmrBoundaries,
+      dirtyFiles
+    )
 
-      const relativeFile = '/' + slash(path.relative(root, filePath))
-      if (hasDeadEnd) {
+    // record dirty files - this is used when HMR requests coming in with
+    // timestamp to determine what files need to be force re-fetched
+    hmrDirtyFilesMap.set(String(timestamp), dirtyFiles)
+
+    const relativeFile = '/' + slash(path.relative(root, filePath))
+    if (hasDeadEnd) {
+      send({
+        type: 'full-reload',
+        path: publicPath,
+        timestamp
+      })
+      console.log(chalk.green(`[vite] `) + `page reloaded.`)
+    } else {
+      hmrBoundaries.forEach((boundary) => {
+        console.log(
+          chalk.green(`[vite:hmr] `) +
+            `${boundary} updated due to change in ${relativeFile}.`
+        )
         send({
-          type: 'full-reload',
-          path: publicPath,
+          type: boundary.endsWith('vue') ? 'vue-reload' : 'js-update',
+          path: boundary,
+          changeSrcPath: publicPath,
           timestamp
         })
-        console.log(chalk.green(`[vite] `) + `page reloaded.`)
-      } else {
-        hmrBoundaries.forEach((boundary) => {
-          console.log(
-            chalk.green(`[vite:hmr] `) +
-              `${boundary} updated due to change in ${relativeFile}.`
-          )
-          send({
-            type: boundary.endsWith('vue') ? 'vue-reload' : 'js-update',
-            path: boundary,
-            changeSrcPath: publicPath,
-            timestamp
-          })
-        })
-      }
-    } else {
-      debugHmr(`no importers for ${publicPath}.`)
+      })
     }
   })
 
diff --git a/src/node/server/serverPluginModuleRewrite.ts b/src/node/server/serverPluginModuleRewrite.ts
index 5ded2dd48250a6..a4f64c02e80f98 100644
--- a/src/node/server/serverPluginModuleRewrite.ts
+++ b/src/node/server/serverPluginModuleRewrite.ts
@@ -72,10 +72,18 @@ export const moduleRewritePlugin: ServerPlugin = ({
         ctx.body = rewriteCache.get(content)
       } else {
         await initLexer
+        // dynamic import may conatin extension-less path,
+        // (.e.g import(runtimePathString))
+        // so we need to normalize importer to ensure it contains extension before we perform hmr analysis.
+        // on the other hand, static import is guaranteed to have extension
+        // because they must all have gone through module rewrite)
+        const importer = resolver.fileToRequest(
+          resolver.requestToFile(ctx.path)
+        )
         ctx.body = rewriteImports(
           root,
           content!,
-          ctx.path,
+          importer,
           resolver,
           ctx.query.t
         )