diff --git a/ChangeLog b/ChangeLog
index 439b1aa4d0..5d4b8c5d38 100755
--- a/ChangeLog
+++ b/ChangeLog
@@ -21,6 +21,8 @@ $Source$
     * header.inc.php3: Don't allow including this file twice.
     * db_details.php3, db_details_importdocsql.php3, export.php3,
       tbl_move_copy.php3, tbl_rename.php3: Added some html quoting.
+    * libraries/tbl_change.js: When ENUM field has just one value, it could
+      not be set to NULL (bug #783533).
 
 2003-08-05 Marc Delisle  <lem9@users.sourceforge.net>
     * libraries/sqlparser.data.php3: bug 779453, wrong count
diff --git a/libraries/tbl_change.js b/libraries/tbl_change.js
index bd924b06a7..c9e13070db 100644
--- a/libraries/tbl_change.js
+++ b/libraries/tbl_change.js
@@ -26,10 +26,16 @@ function nullify(theType, urlField, md5Field)
     // Other "ENUM" field
     else if (theType == 2) {
         var elts     = rowForm.elements['field_' + md5Field + '[]'];
-        var elts_cnt = elts.length;
-        for (var i = 0; i < elts_cnt; i++ ) {
-            elts[i].checked = false;
-        } // end for
+        // when there is just one option in ENUM:
+        if (elts.checked) {
+            elts.checked = false;
+        } else {
+            var elts_cnt = elts.length;
+            for (var i = 0; i < elts_cnt; i++ ) {
+                elts[i].checked = false;
+            } // end for
+
+        } // end if
     }
     // Other field types
     else /*if (theType == 5)*/ {