--- a/java/org/apache/catalina/webresources/AbstractArchiveResourceSet.java	
+++ a/java/org/apache/catalina/webresources/AbstractArchiveResourceSet.java	
@@ -75,7 +75,7 @@ 
             String pathInJar =
                     getInternalPath() + path.substring(webAppMount.length());
             // Always strip off the leading '/' to get the JAR path
-            if (pathInJar.charAt(0) == '/') {
+            if (pathInJar.length() > 0 && pathInJar.charAt(0) == '/') {
                 pathInJar = pathInJar.substring(1);
             }
             Iterator<String> entries = jarFileEntries.keySet().iterator();