diff --git a/WHATSNEW b/WHATSNEW
index 0860cb681..c0b09c6d2 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -76,6 +76,9 @@ Fixed bugs:
 * The <stripjavacomments> filter sometimes removed parts of string
   constants.  Bugzilla Report 17441.
 
+* <antlr> will now recompile your grammar if the supergrammar has
+  changed.  Bugzilla Report 12691.
+
 Other changes:
 --------------
 * Shipped XML parser is now Xerces 2.4.0
diff --git a/docs/manual/OptionalTasks/antlr.html b/docs/manual/OptionalTasks/antlr.html
index fdb20badd..1de0f982f 100644
--- a/docs/manual/OptionalTasks/antlr.html
+++ b/docs/manual/OptionalTasks/antlr.html
@@ -21,10 +21,11 @@
   the grammar file.
 </p>
 <p>
-  This task only invokes ANTLR if the grammar file is newer than the generated
-  files.
+  This task only invokes ANTLR if the grammar file (or the
+  supergrammar specified by the glib attribute) is newer than the
+  generated files.
 </p>
-<p>
+<p>Antlr 2.7.1 Note:
 <i>
   To successfully run ANTLR, your best option is probably to build the whole
   jar with the provided script <b>mkalljar</b> and drop the resulting jar (about 300KB)
@@ -33,6 +34,13 @@
   to your classpath as described in ANTLR <tt>install.html</tt> document.
 </i>
 </p>
+<p>Antlr 2.7.2 Note:
+<i>
+  Instead of the above, you will need antlrall.jar that can be created
+  by the <b>antlr-all.jar</b> target of the Makefile provided with the
+  download.
+</i>
+</p>
 
 <h3>Parameters</h3>
 <table border="1" cellpadding="2" cellspacing="0">
@@ -170,7 +178,7 @@ href="../using.html#arg">Command line arguments</a>.</p>
 </p>
 <hr>
 
-<p align="center">Copyright &copy; 2000-2002 Apache Software Foundation. All rights
+<p align="center">Copyright &copy; 2000-2003 Apache Software Foundation. All rights
 Reserved.</p>
 
 </body>
diff --git a/src/main/org/apache/tools/ant/taskdefs/optional/ANTLR.java b/src/main/org/apache/tools/ant/taskdefs/optional/ANTLR.java
index fc8dd7acf..e513f6a7c 100644
--- a/src/main/org/apache/tools/ant/taskdefs/optional/ANTLR.java
+++ b/src/main/org/apache/tools/ant/taskdefs/optional/ANTLR.java
@@ -276,10 +276,18 @@ public class ANTLR extends Task {
         validateAttributes();
         //TODO: use ANTLR to parse the grammer file to do this.
         File generatedFile = getGeneratedFile();
-        if (target.lastModified() > generatedFile.lastModified()) {
-            log("Compiling " + target + " as it is newer than " 
-                + generatedFile, Project.MSG_VERBOSE);
-
+        boolean targetIsOutOfDate = 
+            target.lastModified() > generatedFile.lastModified();
+        boolean superGrammarIsOutOfDate = superGrammar != null &&
+            (new File(superGrammar).lastModified() > generatedFile.lastModified());
+        if (targetIsOutOfDate || superGrammarIsOutOfDate) {
+            if (targetIsOutOfDate) {
+                log("Compiling " + target + " as it is newer than " 
+                    + generatedFile, Project.MSG_VERBOSE);
+            } else if (superGrammarIsOutOfDate) {
+                log("Compiling " + target + " as " + superGrammar
+                    + " is newer than " + generatedFile, Project.MSG_VERBOSE);
+            }
             populateAttributes();
             commandline.createArgument().setValue(target.toString());