diff --git a/pmd-lang-test/pom.xml b/pmd-lang-test/pom.xml
index e4212445ce..32dc5f267a 100644
--- a/pmd-lang-test/pom.xml
+++ b/pmd-lang-test/pom.xml
@@ -17,7 +17,6 @@
     </parent>
 
     <build>
-        <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
         <testResources>
             <testResource>
                 <directory>${project.basedir}/src/test/resources</directory>
@@ -40,9 +39,21 @@
                             <goal>compile</goal>
                         </goals>
                         <phase>process-sources</phase>
+                        <configuration>
+                            <sourceDirs>
+                                <sourceDir>${project.basedir}/src/main/java</sourceDir>
+                                <sourceDir>${project.basedir}/src/main/kotlin</sourceDir>
+                            </sourceDirs>
+                        </configuration>
                     </execution>
                 </executions>
             </plugin>
+
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
diff --git a/pmd-lang-test/src/main/kotlin/net/sourceforge/pmd/test/AbstractMetricTestRule.java b/pmd-lang-test/src/main/java/net/sourceforge/pmd/test/AbstractMetricTestRule.java
similarity index 100%
rename from pmd-lang-test/src/main/kotlin/net/sourceforge/pmd/test/AbstractMetricTestRule.java
rename to pmd-lang-test/src/main/java/net/sourceforge/pmd/test/AbstractMetricTestRule.java