diff --git a/codegen-client-test/model/error-correction-nullability-test.smithy b/codegen-client-test/model/error-correction-nullability-test.smithy
index 8a125d3004..67bfef5464 100644
--- a/codegen-client-test/model/error-correction-nullability-test.smithy
+++ b/codegen-client-test/model/error-correction-nullability-test.smithy
@@ -102,7 +102,7 @@ apply SayHello @httpResponseTests([{
                                              listValue: [],
                                              mapValue: {},
                                              doubleListValue: []
-                                             document: null
+                                             document: {}
                                              nested: { a: "" }
                                          },
                                          code: 200,
diff --git a/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/http/HttpBindingGenerator.kt b/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/http/HttpBindingGenerator.kt
index c9997ba67a..2ca52895d6 100644
--- a/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/http/HttpBindingGenerator.kt
+++ b/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/http/HttpBindingGenerator.kt
@@ -617,17 +617,26 @@ class HttpBindingGenerator(
             )(this)
         }
 
-        rustBlock("for ${loopVariable.name} in ${context.valueExpression.asRef()}") {
-            this.renderHeaderValue(
-                headerName,
-                loopVariable,
-                model.expectShape(shape.member.target),
-                isMultiValuedHeader = true,
-                timestampFormat,
-                renderErrorMessage,
-                serializeIfDefault = true,
-                shape.member,
-            )
+        rustTemplate(
+            """
+            // Empty vec in header is serialized as the empty string
+            if ${context.valueExpression.name}.is_empty() {
+                builder = builder.header("$headerName", "");
+            }""",
+        )
+        rustBlock("else") {
+            rustBlock("for ${loopVariable.name} in ${context.valueExpression.asRef()}") {
+                this.renderHeaderValue(
+                    headerName,
+                    loopVariable,
+                    model.expectShape(shape.member.target),
+                    isMultiValuedHeader = true,
+                    timestampFormat,
+                    renderErrorMessage,
+                    serializeIfDefault = true,
+                    shape.member,
+                )
+            }
         }
     }
 
@@ -671,14 +680,12 @@ class HttpBindingGenerator(
             val safeName = safeName("formatted")
             rustTemplate(
                 """
-                let $safeName = $formatted;
-                if !$safeName.is_empty() {
-                    let header_value = $safeName;
-                    let header_value: #{HeaderValue} = header_value.parse().map_err(|err| {
-                        #{invalid_field_error:W}
-                    })?;
-                    builder = builder.header("$headerName", header_value);
-                }
+                let header_value = $formatted;
+                let header_value: #{HeaderValue} = header_value.parse().map_err(|err| {
+                    #{invalid_field_error:W}
+                })?;
+                builder = builder.header("$headerName", header_value);
+
                 """,
                 "HeaderValue" to RuntimeType.Http.resolve("HeaderValue"),
                 "invalid_field_error" to renderErrorMessage("header_value"),
diff --git a/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/RpcV2Cbor.kt b/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/RpcV2Cbor.kt
index d3d9800b1a..2832333f59 100644
--- a/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/RpcV2Cbor.kt
+++ b/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/RpcV2Cbor.kt
@@ -112,7 +112,7 @@ open class RpcV2Cbor(val codegenContext: CodegenContext) : Protocol {
     override val defaultTimestampFormat: TimestampFormatTrait.Format = TimestampFormatTrait.Format.EPOCH_SECONDS
 
     override fun additionalRequestHeaders(operationShape: OperationShape): List<Pair<String, String>> =
-        listOf("smithy-protocol" to "rpc-v2-cbor")
+        listOf("smithy-protocol" to "rpc-v2-cbor", "accept" to "application/cbor")
 
     override fun additionalResponseHeaders(operationShape: OperationShape): List<Pair<String, String>> =
         listOf("smithy-protocol" to "rpc-v2-cbor")
diff --git a/gradle.properties b/gradle.properties
index b5e1d59057..38f4db3df4 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -15,7 +15,7 @@ smithy.rs.runtime.crate.unstable.version=0.60.6
 kotlin.code.style=official
 # codegen
 smithyGradlePluginVersion=0.9.0
-smithyVersion=1.51.0
+smithyVersion=1.52.0
 allowLocalDeps=false
 # kotlin
 kotlinVersion=1.9.20