diff --git a/WHATSNEW b/WHATSNEW
index f7c2b9b32..7dff8cb7d 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -56,6 +56,10 @@ Fixed bugs:
  * Ant fails to run if ANT_HOME contains a double-quote character.
    Bugzilla Report 58874
 
+ * Definer's way to parse URLs from classloader breaks with
+   recent Java 9 builds (b108).
+   Bugzilla Report 59130
+
 Other changes:
 --------------
 
diff --git a/src/main/org/apache/tools/ant/taskdefs/Definer.java b/src/main/org/apache/tools/ant/taskdefs/Definer.java
index 8196fa515..e4e3ea38c 100644
--- a/src/main/org/apache/tools/ant/taskdefs/Definer.java
+++ b/src/main/org/apache/tools/ant/taskdefs/Definer.java
@@ -256,7 +256,7 @@ public abstract class Definer extends DefBase {
                 URL url = urls.nextElement();
 
                 int fmt = this.format;
-                if (url.toString().toLowerCase(Locale.ENGLISH).endsWith(".xml")) {
+                if (url.getPath().toLowerCase(Locale.ENGLISH).endsWith(".xml")) {
                     fmt = Format.XML;
                 }