diff --git a/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/generators/http/HttpBindingGenerator.kt b/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/generators/http/HttpBindingGenerator.kt
index 20f2b7fcea100af6d7c7593ab1cffe9b9ac562f8..e61dd831065f3f033110db54c6f146adf81a5817 100644
--- a/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/generators/http/HttpBindingGenerator.kt
+++ b/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/generators/http/HttpBindingGenerator.kt
@@ -25,6 +25,7 @@ import software.amazon.smithy.rust.codegen.rustlang.CargoDependency
 import software.amazon.smithy.rust.codegen.rustlang.RustModule
 import software.amazon.smithy.rust.codegen.rustlang.RustType
 import software.amazon.smithy.rust.codegen.rustlang.RustWriter
+import software.amazon.smithy.rust.codegen.rustlang.asOptional
 import software.amazon.smithy.rust.codegen.rustlang.asType
 import software.amazon.smithy.rust.codegen.rustlang.autoDeref
 import software.amazon.smithy.rust.codegen.rustlang.render
@@ -40,6 +41,7 @@ import software.amazon.smithy.rust.codegen.smithy.RuntimeType
 import software.amazon.smithy.rust.codegen.smithy.generators.operationBuildError
 import software.amazon.smithy.rust.codegen.smithy.generators.redactIfNecessary
 import software.amazon.smithy.rust.codegen.smithy.makeOptional
+import software.amazon.smithy.rust.codegen.smithy.mapRustType
 import software.amazon.smithy.rust.codegen.smithy.protocols.HttpBindingDescriptor
 import software.amazon.smithy.rust.codegen.smithy.protocols.HttpLocation
 import software.amazon.smithy.rust.codegen.smithy.protocols.Protocol
@@ -131,8 +133,8 @@ class HttpBindingGenerator(
 
     fun generateDeserializePrefixHeaderFn(binding: HttpBindingDescriptor): RuntimeType {
         check(binding.location == HttpBinding.Location.PREFIX_HEADERS)
-        val outputT = symbolProvider.toSymbol(binding.member)
-        check(outputT.rustType().stripOuter<RustType.Option>() is RustType.HashMap) { outputT.rustType() }
+        val outputSymbol = symbolProvider.toSymbol(binding.member)
+        check(outputSymbol.rustType().stripOuter<RustType.Option>() is RustType.HashMap) { outputSymbol.rustType() }
         val target = model.expectShape(binding.member.target)
         check(target is MapShape)
         val fnName = "deser_prefix_header_${fnName(operationShape, binding)}"
@@ -146,11 +148,12 @@ class HttpBindingGenerator(
                 deserializeFromHeader(model.expectShape(target.value.target), binding.member)
             }
         }
+        val returnTypeSymbol = outputSymbol.mapRustType { it.asOptional() }
         return RuntimeType.forInlineFun(fnName, httpSerdeModule) { writer ->
             writer.rustBlock(
                 "pub fn $fnName(header_map: &#T::HeaderMap) -> std::result::Result<#T, #T::ParseError>",
                 RuntimeType.http,
-                outputT,
+                returnTypeSymbol,
                 headerUtil
             ) {
                 rust(