diff --git a/WHATSNEW b/WHATSNEW
index 169dafee3..fe612279c 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -197,6 +197,11 @@ Fixed bugs:
 
 Other changes:
 --------------
+* Improve compatibility with GNU Classpath and java versions prior to 1.5. Bugzilla 39027.
+
+* ${ant.core.lib} may now be used to refer to the library containing the
+  Ant classes, for instance useful when compiling tasks.
+
 * Minor performance improvements Bugzilla report 37777
 
 * New task <manifestclasspath> converts a path into a property
diff --git a/src/main/org/apache/tools/ant/util/JavaEnvUtils.java b/src/main/org/apache/tools/ant/util/JavaEnvUtils.java
index 231531ada..26c327245 100644
--- a/src/main/org/apache/tools/ant/util/JavaEnvUtils.java
+++ b/src/main/org/apache/tools/ant/util/JavaEnvUtils.java
@@ -101,7 +101,7 @@ public final class JavaEnvUtils {
             Class.forName("java.lang.CharSequence");
             javaVersion = JAVA_1_4;
             javaVersionNumber++;
-            Class.forName("java.lang.Readable");
+            Class.forName("java.net.Proxy");
             javaVersion = JAVA_1_5;
             javaVersionNumber++;
             Class.forName("java.util.Service");