diff --git a/packages/middleware-retry/src/defaultStrategy.spec.ts b/packages/middleware-retry/src/defaultStrategy.spec.ts
index fb8f69e696aa7..e007a78f9bd2c 100644
--- a/packages/middleware-retry/src/defaultStrategy.spec.ts
+++ b/packages/middleware-retry/src/defaultStrategy.spec.ts
@@ -100,6 +100,16 @@ describe("defaultStrategy", () => {
     });
   });
 
+  it("handles non-standard errors", () => {
+    const nonStandardErrors = [undefined, "foo", { foo: "bar" }, 123, false, null];
+    const maxAttempts = 1;
+    const retryStrategy = new StandardRetryStrategy(() => Promise.resolve(maxAttempts));
+    for (const error of nonStandardErrors) {
+      next = jest.fn().mockRejectedValue(error);
+      expect(retryStrategy.retry(next, { request: { headers: {} } } as any)).rejects.toBeInstanceOf(Error);
+    }
+  });
+
   describe("retryDecider init", () => {
     it("sets defaultRetryDecider if options is undefined", () => {
       const retryStrategy = new StandardRetryStrategy(() => Promise.resolve(maxAttempts));
diff --git a/packages/middleware-retry/src/defaultStrategy.ts b/packages/middleware-retry/src/defaultStrategy.ts
index 5557d32538b37..4b07ae3eb6f5e 100644
--- a/packages/middleware-retry/src/defaultStrategy.ts
+++ b/packages/middleware-retry/src/defaultStrategy.ts
@@ -129,7 +129,8 @@ export class StandardRetryStrategy implements RetryStrategy {
         output.$metadata.totalRetryDelay = totalDelay;
 
         return { response, output };
-      } catch (err) {
+      } catch (e) {
+        const err = asSdkError(e);
         attempts++;
         if (this.shouldRetry(err as SdkError, attempts, maxAttempts)) {
           retryTokenAmount = this.retryQuota.retrieveRetryTokens(err);
@@ -154,3 +155,10 @@ export class StandardRetryStrategy implements RetryStrategy {
     }
   }
 }
+
+const asSdkError = (error: unknown): SdkError => {
+  if (error instanceof Error) return error;
+  if (error instanceof Object) return Object.assign(new Error(), error);
+  if (typeof error === "string") return new Error(error);
+  return new Error(`AWS SDK error wrapper for ${error}`);
+};
diff --git a/packages/smithy-client/src/sdk-error.ts b/packages/smithy-client/src/sdk-error.ts
index 115925155a4b3..683d8d8a14756 100644
--- a/packages/smithy-client/src/sdk-error.ts
+++ b/packages/smithy-client/src/sdk-error.ts
@@ -2,4 +2,4 @@ import { MetadataBearer } from "@aws-sdk/types";
 
 import { SmithyException } from "./exception";
 
-export type SdkError = Error & SmithyException & MetadataBearer;
+export type SdkError = Error & Partial<SmithyException> & Partial<MetadataBearer>;
diff --git a/protocol_tests/aws-ec2/tests/functional/ec2query.spec.ts b/protocol_tests/aws-ec2/tests/functional/ec2query.spec.ts
index 73c4026ead93a..ecc2a7140f7e3 100644
--- a/protocol_tests/aws-ec2/tests/functional/ec2query.spec.ts
+++ b/protocol_tests/aws-ec2/tests/functional/ec2query.spec.ts
@@ -27,8 +27,10 @@ import { Readable } from "stream";
 /**
  * Throws an expected exception that contains the serialized request.
  */
-class EXPECTED_REQUEST_SERIALIZATION_ERROR {
-  constructor(readonly request: HttpRequest) {}
+class EXPECTED_REQUEST_SERIALIZATION_ERROR extends Error {
+  constructor(readonly request: HttpRequest) {
+    super();
+  }
 }
 
 /**
diff --git a/protocol_tests/aws-json/tests/functional/awsjson1_1.spec.ts b/protocol_tests/aws-json/tests/functional/awsjson1_1.spec.ts
index cb3e8fdf50837..eca8059168a83 100644
--- a/protocol_tests/aws-json/tests/functional/awsjson1_1.spec.ts
+++ b/protocol_tests/aws-json/tests/functional/awsjson1_1.spec.ts
@@ -18,8 +18,10 @@ import { Readable } from "stream";
 /**
  * Throws an expected exception that contains the serialized request.
  */
-class EXPECTED_REQUEST_SERIALIZATION_ERROR {
-  constructor(readonly request: HttpRequest) {}
+class EXPECTED_REQUEST_SERIALIZATION_ERROR extends Error {
+  constructor(readonly request: HttpRequest) {
+    super();
+  }
 }
 
 /**
diff --git a/protocol_tests/aws-query/tests/functional/awsquery.spec.ts b/protocol_tests/aws-query/tests/functional/awsquery.spec.ts
index fcd982413c7ce..facdf7b980c2b 100644
--- a/protocol_tests/aws-query/tests/functional/awsquery.spec.ts
+++ b/protocol_tests/aws-query/tests/functional/awsquery.spec.ts
@@ -35,8 +35,10 @@ import { Readable } from "stream";
 /**
  * Throws an expected exception that contains the serialized request.
  */
-class EXPECTED_REQUEST_SERIALIZATION_ERROR {
-  constructor(readonly request: HttpRequest) {}
+class EXPECTED_REQUEST_SERIALIZATION_ERROR extends Error {
+  constructor(readonly request: HttpRequest) {
+    super();
+  }
 }
 
 /**
diff --git a/protocol_tests/aws-restjson/tests/functional/restjson1.spec.ts b/protocol_tests/aws-restjson/tests/functional/restjson1.spec.ts
index 7267b9fa0280a..52c2be52bf30f 100644
--- a/protocol_tests/aws-restjson/tests/functional/restjson1.spec.ts
+++ b/protocol_tests/aws-restjson/tests/functional/restjson1.spec.ts
@@ -51,8 +51,10 @@ import { Readable } from "stream";
 /**
  * Throws an expected exception that contains the serialized request.
  */
-class EXPECTED_REQUEST_SERIALIZATION_ERROR {
-  constructor(readonly request: HttpRequest) {}
+class EXPECTED_REQUEST_SERIALIZATION_ERROR extends Error {
+  constructor(readonly request: HttpRequest) {
+    super();
+  }
 }
 
 /**
diff --git a/protocol_tests/aws-restxml/tests/functional/restxml.spec.ts b/protocol_tests/aws-restxml/tests/functional/restxml.spec.ts
index 0f31c9f4e78a4..3f5567c4bd723 100644
--- a/protocol_tests/aws-restxml/tests/functional/restxml.spec.ts
+++ b/protocol_tests/aws-restxml/tests/functional/restxml.spec.ts
@@ -60,8 +60,10 @@ import { Readable } from "stream";
 /**
  * Throws an expected exception that contains the serialized request.
  */
-class EXPECTED_REQUEST_SERIALIZATION_ERROR {
-  constructor(readonly request: HttpRequest) {}
+class EXPECTED_REQUEST_SERIALIZATION_ERROR extends Error {
+  constructor(readonly request: HttpRequest) {
+    super();
+  }
 }
 
 /**