diff --git a/smithy-openapi/src/main/java/software/amazon/smithy/openapi/fromsmithy/mappers/UnsupportedTraits.java b/smithy-openapi/src/main/java/software/amazon/smithy/openapi/fromsmithy/mappers/UnsupportedTraits.java
index 9d1b49e30cb..87e35719e9b 100644
--- a/smithy-openapi/src/main/java/software/amazon/smithy/openapi/fromsmithy/mappers/UnsupportedTraits.java
+++ b/smithy-openapi/src/main/java/software/amazon/smithy/openapi/fromsmithy/mappers/UnsupportedTraits.java
@@ -4,17 +4,23 @@
  */
 package software.amazon.smithy.openapi.fromsmithy.mappers;
 
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.logging.Logger;
 import java.util.stream.Collectors;
+import software.amazon.smithy.aws.traits.HttpChecksumTrait;
+import software.amazon.smithy.model.shapes.Shape;
 import software.amazon.smithy.model.shapes.ShapeId;
+import software.amazon.smithy.model.traits.EndpointTrait;
+import software.amazon.smithy.model.traits.HostLabelTrait;
 import software.amazon.smithy.model.traits.Trait;
 import software.amazon.smithy.openapi.OpenApiException;
 import software.amazon.smithy.openapi.fromsmithy.Context;
 import software.amazon.smithy.openapi.fromsmithy.OpenApiMapper;
 import software.amazon.smithy.openapi.model.OpenApi;
-import software.amazon.smithy.utils.Pair;
 import software.amazon.smithy.utils.SetUtils;
 import software.amazon.smithy.utils.SmithyInternalApi;
 
@@ -25,7 +31,10 @@
 @SmithyInternalApi
 public final class UnsupportedTraits implements OpenApiMapper {
     private static final Logger LOGGER = Logger.getLogger(UnsupportedTraits.class.getName());
-    private static final Set<String> TRAITS = SetUtils.of("endpoint", "hostLabel", "aws.protocols#httpChecksum");
+    private static final Set<ShapeId> TRAITS = SetUtils.of(
+            EndpointTrait.ID,
+            HostLabelTrait.ID,
+            HttpChecksumTrait.ID);
 
     @Override
     public byte getOrder() {
@@ -34,14 +43,18 @@ public byte getOrder() {
 
     @Override
     public void before(Context<? extends Trait> context, OpenApi.Builder builder) {
-        List<Pair<ShapeId, List<String>>> violations = context.getModel()
-                .shapes()
-                .map(shape -> Pair.of(shape.getId(),
-                        TRAITS.stream()
-                                .filter(trait -> shape.findTrait(trait).isPresent())
-                                .collect(Collectors.toList())))
-                .filter(pair -> pair.getRight().size() > 0)
-                .collect(Collectors.toList());
+        Map<ShapeId, List<ShapeId>> violations = new LinkedHashMap<>();
+        for (Shape shape : context.getModel().toSet()) {
+            List<ShapeId> unsupportedTraits = new ArrayList<>(TRAITS.size());
+            for (ShapeId trait : TRAITS) {
+                if (shape.hasTrait(trait)) {
+                    unsupportedTraits.add(trait);
+                }
+            }
+            if (!unsupportedTraits.isEmpty()) {
+                violations.put(shape.getId(), unsupportedTraits);
+            }
+        }
 
         if (violations.isEmpty()) {
             return;
@@ -49,10 +62,15 @@ public void before(Context<? extends Trait> context, OpenApi.Builder builder) {
 
         StringBuilder message = new StringBuilder(
                 "Encountered unsupported Smithy traits when converting to OpenAPI:");
-        violations.forEach(pair -> message.append(String.format(
-                " (`%s`: [%s])",
-                pair.getLeft(),
-                String.join(",", pair.getRight()))));
+        for (Map.Entry<ShapeId, List<ShapeId>> entry : violations.entrySet()) {
+            message.append(String.format(
+                    " (`%s`: [`%s`])",
+                    entry.getKey(),
+                    entry.getValue()
+                            .stream()
+                            .map(ShapeId::toString)
+                            .collect(Collectors.joining("`, `"))));
+        }
         message.append(". While these traits may still be meaningful to clients and servers using the Smithy "
                 + "model directly, they have no direct corollary in OpenAPI and can not be included in "
                 + "the generated model.");