diff --git a/blockcheck.sh b/blockcheck.sh
index 0713f696..829f51de 100755
--- a/blockcheck.sh
+++ b/blockcheck.sh
@@ -247,7 +247,7 @@ mdig_vars()
 	# $1 - ip version 4/6
 	# $2 - hostname
 
-	hostvar=$(echo $2 | sed -e 's/[\.-/?&#@%*$^~=!()]/_/g')
+	hostvar=$(echo $2 | sed -e 's/[\.-/?&#@%*$^:~=!()]/_/g')
 	cachevar=DNSCACHE_${hostvar}_$1
 	countvar=${cachevar}_COUNT
 	eval count=\$${countvar}