diff --git a/acceptance-tests/acceptance-tests-manifold-systems/pom.xml b/acceptance-tests/acceptance-tests-manifold-systems/pom.xml
index bcac5ee9c..21ab3fa77 100644
--- a/acceptance-tests/acceptance-tests-manifold-systems/pom.xml
+++ b/acceptance-tests/acceptance-tests-manifold-systems/pom.xml
@@ -80,7 +80,7 @@
         <artifactId>maven-surefire-plugin</artifactId>
 
         <configuration>
-          <failIfNoTests>true</failIfNoTests>
+          <failIfNoTests>false</failIfNoTests>
         </configuration>
       </plugin>
     </plugins>
diff --git a/acceptance-tests/acceptance-tests-manifold-systems/src/test/groovy/io/github/ascopes/acceptancetests/manifold/ManifoldPreprocessorTest.groovy b/acceptance-tests/acceptance-tests-manifold-systems/src/test/groovy/io/github/ascopes/acceptancetests/manifold/ManifoldPreprocessorTest.groovy
index 4645bb8ef..0db14e6ff 100644
--- a/acceptance-tests/acceptance-tests-manifold-systems/src/test/groovy/io/github/ascopes/acceptancetests/manifold/ManifoldPreprocessorTest.groovy
+++ b/acceptance-tests/acceptance-tests-manifold-systems/src/test/groovy/io/github/ascopes/acceptancetests/manifold/ManifoldPreprocessorTest.groovy
@@ -17,7 +17,6 @@ package io.github.ascopes.acceptancetests.manifold
 
 import io.github.ascopes.jct.compilers.JctCompiler
 import io.github.ascopes.jct.junit.JavacCompilerTest
-import org.junit.jupiter.api.Disabled
 import org.junit.jupiter.api.DisplayName
 
 import static io.github.ascopes.jct.assertions.JctAssertions.assertThatCompilation
@@ -84,7 +83,6 @@ class ManifoldPreprocessorTest {
     assertThat(greeting).isEqualTo("Hello, World! (symbol was not defined)")
   }
 
-  @Disabled("See https://github.com/manifold-systems/manifold/issues/399")
   @DisplayName("Warning directives produce compiler warnings in JCT")
   @JavacCompilerTest(configurers = [ManifoldPluginConfigurer])
   void warningDirectivesProduceCompilerWarningsInJct(JctCompiler compiler) {