diff --git a/detectors/cds/tools/compare/go_compare.sh b/detectors/cds/tools/compare/go_compare.sh
index b1c8f36..093eaf3 100755
--- a/detectors/cds/tools/compare/go_compare.sh
+++ b/detectors/cds/tools/compare/go_compare.sh
@@ -23,6 +23,10 @@ NeedFile $PrdFile
 set RefType = $RefFile:e
 set PrdType = $PrdFile:e
 
+if ((! -e $LIB_DIR/$RefType.oneliner.awk) || (! -e $LIB_DIR/$PrdType.oneliner.awk)) then
+  Error 1 "file extension should be 'gbk' or 'embl'"
+endif
+
 #
 # parse ref and prediction
 #