diff --git a/src/main/java/io/cryostat/util/IllegalArgumentExceptionMapper.java b/src/main/java/io/cryostat/util/IllegalArgumentExceptionMapper.java
new file mode 100644
index 000000000..6d5a619e9
--- /dev/null
+++ b/src/main/java/io/cryostat/util/IllegalArgumentExceptionMapper.java
@@ -0,0 +1,28 @@
+/*
+ * Copyright The Cryostat Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.cryostat.util;
+
+import jakarta.ws.rs.core.Response;
+import jakarta.ws.rs.ext.ExceptionMapper;
+import jakarta.ws.rs.ext.Provider;
+
+@Provider
+public class IllegalArgumentExceptionMapper implements ExceptionMapper<IllegalArgumentException> {
+    @Override
+    public Response toResponse(IllegalArgumentException exception) {
+        return Response.status(400).build();
+    }
+}
diff --git a/src/test/java/itest/RulesPostJsonIT.java b/src/test/java/itest/RulesPostJsonIT.java
index 003777bda..838ff1f6b 100644
--- a/src/test/java/itest/RulesPostJsonIT.java
+++ b/src/test/java/itest/RulesPostJsonIT.java
@@ -37,7 +37,6 @@
 import org.junit.jupiter.api.Order;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestMethodOrder;
-import org.junit.jupiter.api.condition.DisabledIfEnvironmentVariable;
 
 @QuarkusIntegrationTest
 @TestMethodOrder(OrderAnnotation.class)
@@ -107,12 +106,6 @@ void testAddRuleThrowsWhenMimeUnsupported() throws Exception {
                 ex.getCause().getMessage(), Matchers.equalTo("Unsupported Media Type"));
     }
 
-    @DisabledIfEnvironmentVariable(
-            named = "CI",
-            matches = "true",
-            disabledReason =
-                    "The server 500 seems to cause issues for the next test in the suite, ex. HTTP"
-                            + " connection closed when attempting to POST the next rule definition")
     @Test
     @Order(3)
     void testAddRuleThrowsWhenMimeInvalid() throws Exception {
@@ -131,9 +124,8 @@ void testAddRuleThrowsWhenMimeInvalid() throws Exception {
                 Assertions.assertThrows(
                         ExecutionException.class, () -> response.get(10, TimeUnit.SECONDS));
         MatcherAssert.assertThat(
-                ((HttpException) ex.getCause()).getStatusCode(), Matchers.equalTo(500));
-        MatcherAssert.assertThat(
-                ex.getCause().getMessage(), Matchers.equalTo("Internal Server Error"));
+                ((HttpException) ex.getCause()).getStatusCode(), Matchers.equalTo(400));
+        MatcherAssert.assertThat(ex.getCause().getMessage(), Matchers.equalTo("Bad Request"));
     }
 
     @Test