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 f52f4d38afd..47e1240a091 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
@@ -471,13 +471,15 @@ class HttpBindingGenerator(
     }
 
     private fun RustWriter.renderHeaders(httpBinding: HttpBinding) {
+        check(httpBinding.location == HttpLocation.HEADER)
         val memberShape = httpBinding.member
-        val memberType = model.expectShape(memberShape.target)
+        val targetShape = model.expectShape(memberShape.target)
         val memberSymbol = symbolProvider.toSymbol(memberShape)
         val memberName = symbolProvider.toMemberName(memberShape)
-        ifSet(memberType, memberSymbol, "&input.$memberName") { field ->
-            val isListHeader = memberType is CollectionShape
-            listForEach(memberType, field) { innerField, targetId ->
+
+        ifSet(targetShape, memberSymbol, "&input.$memberName") { field ->
+            val isListHeader = targetShape is CollectionShape
+            listForEach(targetShape, field) { innerField, targetId ->
                 val innerMemberType = model.expectShape(targetId)
                 if (innerMemberType.isPrimitive()) {
                     val encoder = CargoDependency.SmithyTypes(runtimeConfig).asType().member("primitive::Encoder")
@@ -491,9 +493,14 @@ class HttpBindingGenerator(
                         """
                         let header_value = $safeName;
                         let header_value = http::header::HeaderValue::try_from(&*header_value).map_err(|err| {
-                            #{build_error}::InvalidField { field: "$memberName", details: format!("`{}` cannot be used as a header value: {}", &${
-                        memberShape.redactIfNecessary(model, "header_value")
-                        }, err)}
+                            #{build_error}::InvalidField { 
+                                field: "$memberName", 
+                                details: format!(
+                                    "`{}` cannot be used as a header value: {}", 
+                                    &${memberShape.redactIfNecessary(model, "header_value")},
+                                    err,
+                                )
+                            }
                         })?;
                         builder = builder.header("${httpBinding.locationName}", header_value);
                         """,
@@ -505,17 +512,14 @@ class HttpBindingGenerator(
     }
 
     private fun RustWriter.renderPrefixHeader(httpBinding: HttpBinding) {
+        check(httpBinding.location == HttpLocation.PREFIX_HEADERS)
         val memberShape = httpBinding.member
-        val memberType = model.expectShape(memberShape.target)
+        val targetShape = model.expectShape(memberShape.target, MapShape::class.java)
         val memberSymbol = symbolProvider.toSymbol(memberShape)
         val memberName = symbolProvider.toMemberName(memberShape)
-        val target = when (memberType) {
-            is CollectionShape -> model.expectShape(memberType.member.target)
-            is MapShape -> model.expectShape(memberType.value.target)
-            else -> UNREACHABLE("unexpected member for prefix headers: $memberType")
-        }
-        ifSet(memberType, memberSymbol, "&input.$memberName") { field ->
-            val listHeader = memberType is CollectionShape
+        val valueTargetShape = model.expectShape(targetShape.value.target)
+
+        ifSet(targetShape, memberSymbol, "&input.$memberName") { field ->
             rustTemplate(
                 """
                 for (k, v) in $field {
@@ -523,17 +527,19 @@ class HttpBindingGenerator(
                     let header_name = http::header::HeaderName::from_str(&format!("{}{}", "${httpBinding.locationName}", &k)).map_err(|err| {
                         #{build_error}::InvalidField { field: "$memberName", details: format!("`{}` cannot be used as a header name: {}", k, err)}
                     })?;
-                    let header_value = ${headerFmtFun(this, target, memberShape, "v", listHeader)};
+                    let header_value = ${headerFmtFun(this, valueTargetShape, memberShape, "v", isListHeader = false)};
                     let header_value = http::header::HeaderValue::try_from(&*header_value).map_err(|err| {
                         #{build_error}::InvalidField {
                             field: "$memberName",
-                            details: format!("`{}` cannot be used as a header value: {}", ${
-                memberShape.redactIfNecessary(model, "v")
-                }, err)}
+                            details: format!(
+                                "`{}` cannot be used as a header value: {}", 
+                                ${memberShape.redactIfNecessary(model, "v")},
+                                err,
+                            )
+                        }
                     })?;
                     builder = builder.header(header_name, header_value);
                 }
-
                 """,
                 "build_error" to runtimeConfig.operationBuildError(),
             )