diff --git a/api/src/main/java/javax/jdo/JDOHelper.java b/api/src/main/java/javax/jdo/JDOHelper.java
index aa1d0601f..2c62ad3f6 100644
--- a/api/src/main/java/javax/jdo/JDOHelper.java
+++ b/api/src/main/java/javax/jdo/JDOHelper.java
@@ -44,6 +44,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
+import java.util.regex.Pattern;
 import javax.jdo.spi.I18NHelper;
 import javax.jdo.spi.JDOImplHelper;
 import javax.jdo.spi.JDOImplHelper.StateInterrogationBooleanReturn;
@@ -741,6 +742,7 @@ protected static String getClassNameFromURL(URL url) throws IOException {
     InputStream is = openStream(url);
     BufferedReader reader = new BufferedReader(new InputStreamReader(is));
     String line = null;
+    Pattern splitRegex = Pattern.compile("\\s");
     try {
       while ((line = reader.readLine()) != null) {
         line = line.trim();
@@ -748,7 +750,7 @@ protected static String getClassNameFromURL(URL url) throws IOException {
           continue;
         }
         // else assume first line of text is the PMF class name
-        String[] tokens = line.split("\\s");
+        String[] tokens = splitRegex.split(line);
         String pmfClassName = tokens[0];
         int indexOfComment = pmfClassName.indexOf("#");
         if (indexOfComment == -1) {
@@ -971,12 +973,20 @@ public static PersistenceManagerFactory getPersistenceManagerFactory(
   protected static PersistenceManagerFactory invokeGetPersistenceManagerFactoryOnImplementation(
       String pmfClassName, Map<?, ?> overrides, Map<?, ?> properties, ClassLoader cl) {
     try {
-      Class<?> implClass = forName(pmfClassName, true, cl);
+      // load without initializing: no code of the candidate class (which may be named by
+      // the first-match-wins services lookup) runs before the method has been verified
+      Class<?> implClass = forName(pmfClassName, false, cl);
       Method m =
           getMethod(
               implClass,
               "getPersistenceManagerFactory", // NOI18N
               overrides != null ? new Class[] {Map.class, Map.class} : new Class[] {Map.class});
+      if (!PersistenceManagerFactory.class.isAssignableFrom(m.getReturnType())) {
+        // reject before invoking: otherwise the static initializers and method body of an
+        // arbitrary candidate class would run before the type check
+        throw new JDOFatalInternalException(
+            MSG.msg("EXC_GetPMFClassCastException", pmfClassName)); // NOI18N
+      }
       PersistenceManagerFactory pmf =
           (PersistenceManagerFactory)
               invoke(
@@ -1589,7 +1599,13 @@ public static JDOEnhancer getEnhancer(ClassLoader loader) {
         numberOfJDOEnhancers++;
         try {
           String enhancerClassName = getClassNameFromURL(urls.nextElement());
-          Class<?> enhancerClass = forName(enhancerClassName, true, ctrLoader);
+          // load without initializing and verify assignability before running any code of
+          // the candidate class named by the (first-match-wins) services file
+          Class<?> enhancerClass = forName(enhancerClassName, false, ctrLoader);
+          if (!JDOEnhancer.class.isAssignableFrom(enhancerClass)) {
+            throw new JDOFatalUserException(
+                MSG.msg("EXC_GetEnhancerClassNotAssignable", enhancerClassName)); // NOI18N
+          }
           return (JDOEnhancer) enhancerClass.getDeclaredConstructor().newInstance();
         } catch (Exception ex) {
           // remember exceptions from failed enhancer invocations
diff --git a/api/src/main/resources/javax/jdo/Bundle.properties b/api/src/main/resources/javax/jdo/Bundle.properties
index 208ef4561..4d3dd8289 100644
--- a/api/src/main/resources/javax/jdo/Bundle.properties
+++ b/api/src/main/resources/javax/jdo/Bundle.properties
@@ -125,6 +125,9 @@ EXC_GetEnhancerNoValidEnhancerAvailable=\
 There are {0} services entries for the JDOEnhancer; \
 there were no valid JDOEnhancer implementations found in the CLASSPATH. \
 The file META-INF/services/javax.jdo.JDOEnhancer should name the implementation class.
+EXC_GetEnhancerClassNotAssignable=The class "{0}" named in a \
+META-INF/services/javax.jdo.JDOEnhancer resource does not implement \
+javax.jdo.JDOEnhancer. The class was not instantiated.
 MSG_EnhancerUsage=\
 Usage: java -cp <class path> javax.jdo.Enhancer <options> <files>\n\
 options:\n\
diff --git a/api/src/test/java/javax/jdo/JDOHelperServiceValidationTest.java b/api/src/test/java/javax/jdo/JDOHelperServiceValidationTest.java
new file mode 100644
index 000000000..0e273084b
--- /dev/null
+++ b/api/src/test/java/javax/jdo/JDOHelperServiceValidationTest.java
@@ -0,0 +1,80 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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
+ *
+ *     https://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 javax.jdo;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.util.Collections;
+import java.util.Enumeration;
+import javax.jdo.util.AbstractTest;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests that service-file discovery verifies the candidate class before running any of its code: a
+ * class named by a META-INF/services/javax.jdo.JDOEnhancer resource that does not implement
+ * JDOEnhancer must be rejected without executing its static initializer or constructor.
+ */
+class JDOHelperServiceValidationTest extends AbstractTest {
+
+  /** Set by NotAnEnhancer's static and instance initializers; must remain false. */
+  static volatile boolean notAnEnhancerCodeRan = false;
+
+  /** A services-file candidate that is not a JDOEnhancer. */
+  public static class NotAnEnhancer {
+    static {
+      notAnEnhancerCodeRan = true;
+    }
+
+    public NotAnEnhancer() {
+      notAnEnhancerCodeRan = true;
+    }
+  }
+
+  @Test
+  void testGetEnhancerRejectsNonEnhancerWithoutRunningItsCode() throws IOException {
+    File services = File.createTempFile("javax.jdo.JDOEnhancer", ".services");
+    services.deleteOnExit();
+    Files.write(
+        services.toPath(), (NotAnEnhancer.class.getName() + "\n").getBytes(StandardCharsets.UTF_8));
+    final URL servicesURL = services.toURI().toURL();
+
+    // a loader whose only JDOEnhancer services entry names NotAnEnhancer
+    ClassLoader loader =
+        new ClassLoader(getClass().getClassLoader()) {
+          @Override
+          public Enumeration<URL> getResources(String name) throws IOException {
+            if ("META-INF/services/javax.jdo.JDOEnhancer".equals(name)) {
+              return Collections.enumeration(Collections.singletonList(servicesURL));
+            }
+            return super.getResources(name);
+          }
+        };
+
+    Assertions.assertThrows(
+        JDOFatalUserException.class,
+        () -> JDOHelper.getEnhancer(loader),
+        "getEnhancer with only a non-enhancer candidate should fail");
+    Assertions.assertFalse(
+        notAnEnhancerCodeRan,
+        "Code of the non-enhancer candidate must not run before the type check");
+  }
+}