diff --git a/http/etag.ts b/http/etag.ts
index 32cc88d572b6..12db49e9cd4b 100644
--- a/http/etag.ts
+++ b/http/etag.ts
@@ -158,7 +158,11 @@ export async function eTag(
       ? calcFileInfo(entity, options)
       : calcEntity(entity, options));
 
-  return tag ? weak ? `W/"${tag}"` : `"${tag}"` : undefined;
+  if (!tag) {
+    return undefined;
+  }
+
+  return weak ? `W/"${tag}"` : `"${tag}"`;
 }
 
 const STAR_REGEXP = /^\s*\*\s*$/;
diff --git a/http/etag_test.ts b/http/etag_test.ts
index 3540c28742dd..5aaefe17997f 100644
--- a/http/etag_test.ts
+++ b/http/etag_test.ts
@@ -147,3 +147,17 @@ Deno.test({
     }
   },
 });
+
+Deno.test({
+  name: "eTag() returns undefined when calcFileInfo returns undefined",
+  async fn() {
+    {
+      const result = await eTag({
+        mtime: null,
+        size: 1024,
+      });
+
+      assert(result === undefined);
+    }
+  },
+});