diff --git a/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/protocols/parse/JsonParserGenerator.kt b/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/protocols/parse/JsonParserGenerator.kt
index d963b9684c480f4d3e95a08d216f2d0d85f33df6..739f0a93e6a402572d420b24b379dcfd5c1b86f0 100644
--- a/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/protocols/parse/JsonParserGenerator.kt
+++ b/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/protocols/parse/JsonParserGenerator.kt
@@ -370,7 +370,7 @@ class JsonParserGenerator(
                         if (StructureGenerator.fallibleBuilder(shape, symbolProvider)) {
                             rustTemplate(
                                 """.map_err(|err| #{Error}::new(
-                                #{ErrorReason}::Custom(format!({}, err).into()), None)
+                                #{ErrorReason}::Custom(format!("{}", err).into()), None)
                                 )?""",
                                 *codegenScope
                             )