diff --git a/utility/src/main/java/org/eclipse/persistence/tools/workbench/utility/Classpath.java b/utility/src/main/java/org/eclipse/persistence/tools/workbench/utility/Classpath.java
index e2db3391..433ff2d3 100644
--- a/utility/src/main/java/org/eclipse/persistence/tools/workbench/utility/Classpath.java
+++ b/utility/src/main/java/org/eclipse/persistence/tools/workbench/utility/Classpath.java
@@ -345,7 +345,7 @@ public static String locationFor(Class javaClass) {
             return path.substring(0, path.length() - convertToClassFileName(javaClass).length() - 1);
         } else if ("jrt".equals(protocol)) {
             // jdk9 - jrt:/java.base/java/lang/Object.class
-            return path.substring(0, path.indexOf('/', 5));
+            return path.substring(0, path.indexOf(File.separatorChar, 5));
         }
 
         throw new IllegalStateException(url.toString());