diff --git a/build_manpage.sh b/build_manpage.sh
index 7914fc2..d0d44d1 100755
--- a/build_manpage.sh
+++ b/build_manpage.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-if [[ -n "${1}" ]]; then
+if [ -n "${1}" ]; then
     dir="$(dirname ${0})"
     cp -vf ${dir}/whyblocked.1.adoc .
     sed -Ei "s/(Revision: +)[0-9]+\.[0-9]\.[0-9]/\1${1}/" whyblocked.1.adoc