diff --git a/ant/org.eclipse.ant.launching/src/org/eclipse/ant/internal/launching/launchConfigurations/AntClasspathProvider.java b/ant/org.eclipse.ant.launching/src/org/eclipse/ant/internal/launching/launchConfigurations/AntClasspathProvider.java
index 4736e94..b415de1 100644
--- a/ant/org.eclipse.ant.launching/src/org/eclipse/ant/internal/launching/launchConfigurations/AntClasspathProvider.java
+++ b/ant/org.eclipse.ant.launching/src/org/eclipse/ant/internal/launching/launchConfigurations/AntClasspathProvider.java
@@ -36,6 +36,9 @@
 			IRuntimeClasspathEntry jreEntry = null;
 			try {
 				jreEntry = JavaRuntime.computeJREEntry(configuration);
+				if (jreEntry != null) {
+					jreEntry.setClasspathProperty(IRuntimeClasspathEntry.STANDARD_CLASSES);
+				}
 			}
 			catch (CoreException e) {
 				// not a java project