diff --git a/README.md b/README.md
index 60a2a08..8479bcd 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,8 @@ Options:
   -l MINLEN, --min-len=MINLEN
                         print BED feature only if its length is bigger (or equal
                         to) than MINLELN (default: 1)
+  -z MINCTG, --min-ctg-len=MINCTG
+                        skip reference sequences having size less or equal to MINCTG
   -d, --discard-invalid-alignments
                         skip duplicates, failed QC, and non primary alignment,
                         minq>0 (or user-defined if higher) (default: 0)
diff --git a/binaries/build_osx.sh b/binaries/build_osx.sh
index 87ed291..b6670f4 100755
--- a/binaries/build_osx.sh
+++ b/binaries/build_osx.sh
@@ -1,6 +1,7 @@
 #!/bin/bash
 if [ ! -d "$HOME/miniconda3" ]; then
 	echo "MINICONDA not found in $HOME/miniconda3"
+	echo "Install miniconda, then get bamtools from bioconda."
 	exit 1;
 fi
 if [ ! -e "$HOME/miniconda3/lib/libbamtools.a" ]; then
diff --git a/binaries/build_ubuntu.sh b/binaries/build_ubuntu.sh
index d6d86a9..73c0b58 100755
--- a/binaries/build_ubuntu.sh
+++ b/binaries/build_ubuntu.sh
@@ -1,5 +1,15 @@
 #!/bin/bash
 
+if [ ! -e "/usr/lib/x86_64-linux-gnu/libbamtools.a" ]; then
+	echo "Bamtools not found at: /usr/lib/x86_64-linux-gnu/libbamtools.a"
+	exit 1
+fi
+
+if [ ! -e "/usr/lib/gcc/x86_64-linux-gnu/5/libstdc++.a" ]; then
+	echo "Stdlib not found at: /usr/lib/gcc/x86_64-linux-gnu/5/libstdc++.a"
+	exit 1
+fi
+
 set -euxo pipefail
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null && pwd )"
 cd "$SCRIPT_DIR/.."
diff --git a/binaries/covtobed_mac b/binaries/covtobed_mac
index 9f4b44f..2bcd65e 100755
Binary files a/binaries/covtobed_mac and b/binaries/covtobed_mac differ
diff --git a/binaries/covtobed_mac_debug b/binaries/covtobed_mac_debug
index 1c84a2f..d8341c1 100755
Binary files a/binaries/covtobed_mac_debug and b/binaries/covtobed_mac_debug differ