diff --git a/CHANGES b/CHANGES
index 2692730e66..f901074e55 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,5 @@
 
-2.4-225 | 2015-12-18 11:40:43 -0800
+2.4-226 | 2015-12-18 12:58:36 -0800
 
   * Update host name in windows-version-detection.bro. (Aaron Eppert)
 
@@ -10,6 +10,8 @@
 
   * StartTLS support for IRC. (Johanna Amann)
 
+  * Adding usage guard to canonifier script. (Robin Sommer)
+
 2.4-217 | 2015-12-04 16:50:46 -0800
 
   * SIP scripts code cleanup. (Seth Hall)
diff --git a/VERSION b/VERSION
index 112d5bcd65..0808996833 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.4-225
+2.4-226
diff --git a/testing/scripts/diff-canonifier-external b/testing/scripts/diff-canonifier-external
index 611d7c7baf..bd91924d48 100755
--- a/testing/scripts/diff-canonifier-external
+++ b/testing/scripts/diff-canonifier-external
@@ -2,6 +2,11 @@
 #
 # Default canonifier used with the trace-based tests in testing/external/*.
 
+if [ $# != 1 ]; then
+    echo "usage: `basename $0` <filename>"
+    exit 1
+fi
+
 filename=`basename $1`
 
 addl="cat"