diff --git a/src/main/org/apache/tools/ant/filters/ClassConstants.java b/src/main/org/apache/tools/ant/filters/ClassConstants.java
index 297edab8e..0bf76497d 100644
--- a/src/main/org/apache/tools/ant/filters/ClassConstants.java
+++ b/src/main/org/apache/tools/ant/filters/ClassConstants.java
@@ -101,7 +101,7 @@ public final class ClassConstants
             }
         } else {
             final String clazz = readFully();
-            if (clazz == null && clazz.length() != 0) {
+            if (clazz == null || clazz.length() == 0) {
                 ch = -1;
             } else {
                 final byte[] bytes = clazz.getBytes("ISO-8859-1");