diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/internal/JavaAstProcessor.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/internal/JavaAstProcessor.java
index 335d3c8a53..913f53b36e 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/internal/JavaAstProcessor.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/internal/JavaAstProcessor.java
@@ -43,6 +43,11 @@ import net.sourceforge.pmd.lang.java.types.internal.infer.TypeInferenceLogger.Ve
  */
 public final class JavaAstProcessor {
 
+    /**
+     * FIXME get rid of that, this prevents both ClassLoader and TypeSystem
+     *  to be garbage-collected, which is an important memory leak. Will be
+     *  fixed by https://github.com/pmd/pmd/issues/3782 (Language Lifecycle)
+     */
     private static final Map<ClassLoader, TypeSystem> TYPE_SYSTEMS = new IdentityHashMap<>();
     private static final Level INFERENCE_LOG_LEVEL;
 
diff --git a/pmd-test/src/main/java/net/sourceforge/pmd/testframework/RuleTst.java b/pmd-test/src/main/java/net/sourceforge/pmd/testframework/RuleTst.java
index e3a35697ac..d9ceed4b85 100644
--- a/pmd-test/src/main/java/net/sourceforge/pmd/testframework/RuleTst.java
+++ b/pmd-test/src/main/java/net/sourceforge/pmd/testframework/RuleTst.java
@@ -56,7 +56,12 @@ import net.sourceforge.pmd.util.datasource.DataSource;
 public abstract class RuleTst {
     private final DocumentBuilder documentBuilder;
 
+    /** Use a single classloader for all tests. */
+    private final ClassLoader classpathClassLoader;
+
     public RuleTst() {
+        classpathClassLoader = makeClassPathClassLoader();
+
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
         Schema schema;
@@ -87,6 +92,19 @@ public abstract class RuleTst {
         }
     }
 
+    private ClassLoader makeClassPathClassLoader() {
+        final ClassLoader classpathClassLoader;
+        PMDConfiguration config = new PMDConfiguration();
+        try {
+            config.prependClasspath(".");
+        } catch (IOException ignored) {
+
+        }
+        classpathClassLoader = config.getClassLoader();
+        return classpathClassLoader;
+    }
+
+
     protected void setUp() {
         // This method is intended to be overridden by subclasses.
     }
@@ -263,7 +281,10 @@ public abstract class RuleTst {
 
             if (isUseAuxClasspath) {
                 // configure the "auxclasspath" option for unit testing
-                configuration.prependClasspath(".");
+                // we share a single classloader so that pmd-java doesn't create
+                // a new TypeSystem for every test. This problem will go
+                // away when languages have a lifecycle.
+                configuration.setClassLoader(classpathClassLoader);
             } else {
                 // simple class loader, that doesn't delegate to parent.
                 // this allows us in the tests to simulate PMD run without