diff --git a/usr.bin/man/man.sh b/usr.bin/man/man.sh
index 03803b77746..af638527f49 100755
--- a/usr.bin/man/man.sh
+++ b/usr.bin/man/man.sh
@@ -201,6 +201,10 @@ decho() {
 # Returns true if glob resolves to a real file and store the first
 # found filename in the variable $found
 exists() {
+	if [ -z "$1" ]; then
+		return 1
+	fi
+
 	local IFS
 
 	# Don't accidentally inherit callers IFS (breaks perl manpages)