diff --git a/build.sh b/build.sh
index 1f05fb6..e5559bf 100755
--- a/build.sh
+++ b/build.sh
@@ -1,10 +1,40 @@
 #!/bin/bash
 
-set -eu
+set -u
+
+ip_in_block() {
+    local ip="$1"
+    local block="$2"
+    local ip2octets=( ${ip//./ } )
+    local network=( ${block%/*} )
+    local network2octets=( ${network//./ } )
+    local mask="${block#*/}"
+    local netmask=$(( 0xFFFFFFFF << (32 - mask) ))
+    local network_val=0
+    local ip_val=0
+
+    # HACK: as we don't go lower than /8 , exit quickly
+    if [ ${network2octets[0]} != ${ip2octets[0]} ]; then
+      return -1
+    fi
+
+    for octet in 0 1 2 3; do
+        network_val=$((network_val << 8 | network2octets[octet]))
+        ip_val=$((ip_val << 8 | ip2octets[octet]))
+        #echo "$network_val - $ip_val"
+    done
+
+    network_val=$((network_val & netmask))
+    ip_val=$((ip_val & netmask))
+
+    [ "$network_val" -eq "$ip_val" ]
+}
 
 FILE_SOURCE=source
 TARGET=public/blocklist.ipset
-mkdir -p public
+TMPFILE=tmpfile
+mkdir -p `dirname $TARGET`
+[ -f "$TMPFILE" ] && rm -f $TMPFILE
 
 # if no changes pending, everything is commited
 if [ -z "`git status -s`" ]; then
@@ -14,10 +44,32 @@ else
   DATE=`date`
   COMMIT="latest"
 fi
-ENTRIES=`grep -ve '^#' -ve '^$' $FILE_SOURCE | wc -l`
+
+# Generate entry file
+grep -ve '^#' -ve '^$' $FILE_SOURCE | cut -d ' ' -f1 > $TMPFILE
+
+if [ -z "${DONT_CLEAN}" ]; then
+  CIDR_LIST=`grep '/' $TMPFILE`
+
+  # Remove single IP addresses if matching in CIDR blocks
+  for BLOCK in $CIDR_LIST; do
+    NET="${BLOCK%/*}"
+    CIDR="${BLOCK#*/}"
+    #echo "DEBUG: $BLOCK"
+    while read -r line; do
+      if [[ "$line" == *"/"* ]]; then continue; fi
+      if ip_in_block "$line" "$BLOCK"; then
+        sed -i "/^${line}$/d" $TMPFILE
+      fi
+    done < $TMPFILE
+  done
+fi
+
+ENTRIES=`cat $TMPFILE | wc -l`
 
 export DATE COMMIT ENTRIES
 
 envsubst < template > $TARGET
 
-grep -ve '^#' -ve '^$' $FILE_SOURCE | sort -t . -k 1,1n -k 2,2n -k 3,3n -k 4,4n | cut -d ' ' -f1 >> $TARGET
+cat $TMPFILE | sort -t . -k 1,1n -k 2,2n -k 3,3n -k 4,4n | cut -d ' ' -f1 >> $TARGET
+[ -f "$TMPFILE" ] && rm -f $TMPFILE