diff --git a/CHANGELOG.next.toml b/CHANGELOG.next.toml
index fc4c4c2578b5c5f185517bd30b00e87999da307c..b4f5b3b8b6c9abf8c87eead5c93d03e4b93133b6 100644
--- a/CHANGELOG.next.toml
+++ b/CHANGELOG.next.toml
@@ -9,4 +9,10 @@
 # message = "Fix typos in module documentation for generated crates"
 # references = ["smithy-rs#920"]
 # meta = { "breaking" = false, "tada" = false, "bug" = false, "target" = "client | server | all"}
-# author = "rcoh"
\ No newline at end of file
+# author = "rcoh"
+
+[[aws-sdk-rust]]
+message = "Fix aws-sdk-rust#930 (PutSnapshotBlock)"
+references = ["smithy-rs#3126", "aws-sdk-rust#930"]
+meta = { "breaking" = false, "tada" = false, "bug" = true }
+author = "rcoh"
diff --git a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/SigV4AuthDecorator.kt b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/SigV4AuthDecorator.kt
index 46f070e18e26cadf438855ed57e15946973e80d6..b56fa513bb4d90db4f64bc75ef063371133f0f1f 100644
--- a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/SigV4AuthDecorator.kt
+++ b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/SigV4AuthDecorator.kt
@@ -226,7 +226,7 @@ private class AuthOperationCustomization(private val codegenContext: ClientCodeg
                 if (authSchemes.containsKey(SigV4Trait.ID)) {
                     val unsignedPayload = section.operationShape.hasTrait<UnsignedPayloadTrait>()
                     val doubleUriEncode = unsignedPayload || !disableDoubleEncode(codegenContext.serviceShape)
-                    val contentSha256Header = needsAmzSha256(codegenContext.serviceShape)
+                    val contentSha256Header = needsAmzSha256(codegenContext.serviceShape) || unsignedPayload
                     val normalizeUrlPath = !disableUriPathNormalization(codegenContext.serviceShape)
                     rustTemplate(
                         """
diff --git a/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/SigV4AuthDecoratorTest.kt b/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/SigV4AuthDecoratorTest.kt
new file mode 100644
index 0000000000000000000000000000000000000000..64f35d197fadaee984f3176ae8290b366bbcbb38
--- /dev/null
+++ b/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/SigV4AuthDecoratorTest.kt
@@ -0,0 +1,64 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package software.amazon.smithy.rustsdk
+
+import org.junit.jupiter.api.Test
+import software.amazon.smithy.rust.codegen.core.testutil.asSmithyModel
+
+class SigV4AuthDecoratorTest {
+    private val modelWithSigV4AuthScheme = """
+        namespace test
+
+        use aws.auth#sigv4
+        use aws.api#service
+        use aws.protocols#restJson1
+        use smithy.rules#endpointRuleSet
+        use aws.auth#unsignedPayload
+        use smithy.test#httpRequestTests
+
+        @auth([sigv4])
+        @sigv4(name: "dontcare")
+        @restJson1
+        @endpointRuleSet({
+            "version": "1.0",
+            "rules": [{ "type": "endpoint", "conditions": [], "endpoint": { "url": "https://example.com" } }],
+            "parameters": {
+                "endpoint": { "required": true, "type": "string", "builtIn": "SDK::Endpoint" },
+            }
+        })
+        @service(sdkId: "dontcare")
+        service TestService { version: "2023-01-01", operations: [SomeOperation] }
+        structure SomeOutput { something: String }
+
+        structure SomeInput {
+            @httpPayload
+            something: Bytestream
+         }
+
+        @streaming
+        blob Bytestream
+
+        @httpRequestTests([{
+            id: "unsignedPayload",
+            protocol: restJson1,
+            method: "POST",
+            uri: "/",
+            params: {
+                something: "hello"
+            },
+            headers: {
+                "x-amz-content-sha256": "UNSIGNED-PAYLOAD",
+            },
+        }])
+        @unsignedPayload
+        @http(uri: "/", method: "POST")
+        operation SomeOperation { input: SomeInput, output: SomeOutput }
+    """.asSmithyModel()
+
+    @Test
+    fun unsignedPayloadSetsCorrectHeader() {
+        awsSdkIntegrationTest(modelWithSigV4AuthScheme) { _, _ -> }
+    }
+}