diff --git a/packages/middleware-flexible-checksums/src/constants.ts b/packages/middleware-flexible-checksums/src/constants.ts
index eaa64c32ca396..688febe373994 100644
--- a/packages/middleware-flexible-checksums/src/constants.ts
+++ b/packages/middleware-flexible-checksums/src/constants.ts
@@ -53,7 +53,7 @@ export const DEFAULT_RESPONSE_CHECKSUM_VALIDATION = RequestChecksumCalculation.W
  */
 export enum ChecksumAlgorithm {
   /**
-   * @deprecated Use {@link ChecksumAlgorithm.CRC32} instead.
+   * @deprecated Use {@link ChecksumAlgorithm.SHA256} instead.
    */
   MD5 = "MD5",
   CRC32 = "CRC32",
@@ -73,7 +73,7 @@ export enum ChecksumLocation {
 /**
  * @internal
  */
-export const DEFAULT_CHECKSUM_ALGORITHM = ChecksumAlgorithm.CRC32;
+export const DEFAULT_CHECKSUM_ALGORITHM = ChecksumAlgorithm.SHA256;
 
 /**
  * @internal
diff --git a/private/aws-middleware-test/src/middleware-serde.spec.ts b/private/aws-middleware-test/src/middleware-serde.spec.ts
index 9049f5bb0591b..7516e7c1b53c5 100644
--- a/private/aws-middleware-test/src/middleware-serde.spec.ts
+++ b/private/aws-middleware-test/src/middleware-serde.spec.ts
@@ -27,7 +27,7 @@ describe("middleware-serde", () => {
           "x-amz-acl": "private",
           "content-length": "509",
           Expect: "100-continue",
-          "x-amz-checksum-crc32": "XnKFaw==",
+          "x-amz-checksum-sha256": "wKiXgOGqxd+hdgTp4lYW57q7oLZV2xib5JtMNSVDuyI=",
           host: "s3.us-west-2.amazonaws.com",
           "x-amz-content-sha256": "c0a89780e1aac5dfa17604e9e25616e7babba0b655db189be49b4c352543bb22",
         },