diff --git a/util/git-hooks/commit-msg b/util/git-hooks/commit-msg
index 3b3d541..b9217e0 100755
--- a/util/git-hooks/commit-msg
+++ b/util/git-hooks/commit-msg
@@ -6,6 +6,10 @@
 #
 # Copyright (C) 2009 The Android Open Source Project
 #
+# Any other changes including test_duplicate_signoffs_acks
+#
+# Copyright (C) 2017 Stefan Tauner
+#
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
@@ -188,5 +192,18 @@
 	git hash-object -t commit --stdin
 }
 
+# Test for duplicate signoffs/acks
+test_duplicate_signoffs_acks() {
+	test "" = "$(grep -i '^(Signed-off-by|Acked-by): ' "$MSG" |
+		 sort | uniq -c | sed -e '/^[[:space:]]*1[[:space:]]/d')" || {
+		echo "Duplicate Signed-off-by or Acked-by lines." >&2
+		exit 1
+	}
+}
 
-add_ChangeId
+main() {
+	test_duplicate_signoffs_acks
+	add_ChangeId
+}
+
+main