diff --git a/aws/client/aws-client-awsjson/src/main/java/software/amazon/smithy/java/aws/client/awsjson/AwsJson1Protocol.java b/aws/client/aws-client-awsjson/src/main/java/software/amazon/smithy/java/aws/client/awsjson/AwsJson1Protocol.java
index b28b6b6392..f5fd8b8e64 100644
--- a/aws/client/aws-client-awsjson/src/main/java/software/amazon/smithy/java/aws/client/awsjson/AwsJson1Protocol.java
+++ b/aws/client/aws-client-awsjson/src/main/java/software/amazon/smithy/java/aws/client/awsjson/AwsJson1Protocol.java
@@ -31,8 +31,12 @@ public AwsJson1Protocol(ShapeId service) {
     }
 
     private static ShapeId extractErrorType(Document document, String namespace) {
+        // Per the awsJson1_0 spec, the __type discriminator may carry an over-the-wire namespace
+        // like "com.amazonaws.dynamodb.v20120810#ResourceNotFoundException" that doesn't match
+        // the model's namespace. Strip the namespace and let parseDiscriminator re-attach the
+        // service's namespace so registry lookup succeeds.
         return DocumentDeserializer.parseDiscriminator(
-                ErrorTypeUtils.removeUri(ErrorTypeUtils.readTypeAndCode(document)),
+                ErrorTypeUtils.removeNamespaceAndUri(ErrorTypeUtils.readTypeAndCode(document)),
                 namespace);
     }