diff --git a/packages/middleware-flexible-checksums/src/getCrc32ChecksumAlgorithmFunction.ts b/packages/middleware-flexible-checksums/src/getCrc32ChecksumAlgorithmFunction.ts
index 3803ccfdedae..92046dfdd7a1 100644
--- a/packages/middleware-flexible-checksums/src/getCrc32ChecksumAlgorithmFunction.ts
+++ b/packages/middleware-flexible-checksums/src/getCrc32ChecksumAlgorithmFunction.ts
@@ -3,26 +3,28 @@ import { numToUint8 } from "@aws-crypto/util";
 import { Checksum } from "@smithy/types";
 import * as zlib from "zlib";
 
+class NodeCrc32 implements Checksum {
+  private checksum = 0;
+
+  update(data: Uint8Array) {
+    // @ts-expect-error crc32 is defined only for Node.js >=v20.15.0 and >=v22.2.0.
+    this.checksum = zlib.crc32(data, this.checksum);
+  }
+
+  async digest() {
+    return numToUint8(this.checksum);
+  }
+
+  reset() {
+    this.checksum = 0;
+  }
+}
+
 export const getCrc32ChecksumAlgorithmFunction = () => {
   // @ts-expect-error crc32 is defined only for Node.js >=v20.15.0 and >=v22.2.0.
   if (typeof zlib.crc32 === "undefined") {
     return AwsCrc32;
   }
 
-  return class NodeCrc32 implements Checksum {
-    checksum = 0;
-
-    update(data: Uint8Array) {
-      // @ts-expect-error crc32 is defined only for Node.js >=v20.15.0 and >=v22.2.0.
-      this.checksum = zlib.crc32(data, this.checksum);
-    }
-
-    async digest() {
-      return numToUint8(this.checksum);
-    }
-
-    reset() {
-      this.checksum = 0;
-    }
-  };
+  return NodeCrc32;
 };
diff --git a/packages/middleware-flexible-checksums/src/selectChecksumAlgorithmFunction.spec.ts b/packages/middleware-flexible-checksums/src/selectChecksumAlgorithmFunction.spec.ts
index e3c41477aea4..7d1e7b785e81 100644
--- a/packages/middleware-flexible-checksums/src/selectChecksumAlgorithmFunction.spec.ts
+++ b/packages/middleware-flexible-checksums/src/selectChecksumAlgorithmFunction.spec.ts
@@ -2,7 +2,7 @@ import { AwsCrc32c } from "@aws-crypto/crc32c";
 import { describe, expect, test as it, vi } from "vitest";
 
 import { ChecksumAlgorithm } from "./constants";
-// import { getCrc32ChecksumAlgorithmFunction } from "./getCrc32ChecksumAlgorithmFunction";
+import { getCrc32ChecksumAlgorithmFunction } from "./getCrc32ChecksumAlgorithmFunction";
 import { selectChecksumAlgorithmFunction } from "./selectChecksumAlgorithmFunction";
 
 describe(selectChecksumAlgorithmFunction.name, () => {
@@ -14,7 +14,7 @@ describe(selectChecksumAlgorithmFunction.name, () => {
 
   it.each([
     [ChecksumAlgorithm.MD5, mockConfig.md5],
-    // [ChecksumAlgorithm.CRC32, getCrc32ChecksumAlgorithmFunction()],
+    [ChecksumAlgorithm.CRC32, getCrc32ChecksumAlgorithmFunction()],
     [ChecksumAlgorithm.CRC32C, AwsCrc32c],
     [ChecksumAlgorithm.SHA1, mockConfig.sha1],
     [ChecksumAlgorithm.SHA256, mockConfig.sha256],