diff --git a/bin/jdnssec-dstool b/bin/jdnssec-dstool
index c874637..333cce2 100755
--- a/bin/jdnssec-dstool
+++ b/bin/jdnssec-dstool
@@ -3,7 +3,10 @@
 thisdir=`dirname $0`
 basedir=`cd $thisdir/..; pwd`
 
-ulimit -n `ulimit -H -n`
+ulimit_max=`ulimit -H -n`
+if [ $ulimit_max != "unlimited" ]; then
+    ulimit -n $ulimit_max
+fi
 
 # set the classpath
 for i in $basedir/lib/*.jar $basedir/lib/*.zip $basedir/build/lib/*.jar; do
diff --git a/bin/jdnssec-keygen b/bin/jdnssec-keygen
index 31384fb..d51a40e 100755
--- a/bin/jdnssec-keygen
+++ b/bin/jdnssec-keygen
@@ -1,9 +1,12 @@
-#! /bin/sh
+f#! /bin/sh
 
 thisdir=`dirname $0`
 basedir=`cd $thisdir/..; pwd`
 
-ulimit -n `ulimit -H -n`
+ulimit_max=`ulimit -H -n`
+if [ $ulimit_max != "unlimited" ]; then
+    ulimit -n $ulimit_max
+fi
 
 # set the classpath
 for i in $basedir/lib/*.jar $basedir/lib/*.zip $basedir/build/lib/*.jar; do
diff --git a/bin/jdnssec-signzone b/bin/jdnssec-signzone
index e729d31..7ce8b60 100755
--- a/bin/jdnssec-signzone
+++ b/bin/jdnssec-signzone
@@ -3,7 +3,10 @@
 thisdir=`dirname $0`
 basedir=`cd $thisdir/..; pwd`
 
-ulimit -n `ulimit -H -n`
+ulimit_max=`ulimit -H -n`
+if [ $ulimit_max != "unlimited" ]; then
+    ulimit -n $ulimit_max
+fi
 
 # set the classpath
 for i in $basedir/lib/*.jar $basedir/lib/*.zip $basedir/build/lib/*.jar; do
diff --git a/bin/jdnssec-verifyzone b/bin/jdnssec-verifyzone
index b0ca825..dca9aec 100755
--- a/bin/jdnssec-verifyzone
+++ b/bin/jdnssec-verifyzone
@@ -3,7 +3,10 @@
 thisdir=`dirname $0`
 basedir=`cd $thisdir/..; pwd`
 
-ulimit -n `ulimit -H -n`
+ulimit_max=`ulimit -H -n`
+if [ $ulimit_max != "unlimited" ]; then
+    ulimit -n $ulimit_max
+fi
 
 # set the classpath
 for i in $basedir/lib/*.jar $basedir/lib/*.zip $basedir/build/lib/*.jar; do
diff --git a/bin/jdnssec-zoneformat b/bin/jdnssec-zoneformat
index 876e42b..6e0a153 100755
--- a/bin/jdnssec-zoneformat
+++ b/bin/jdnssec-zoneformat
@@ -3,7 +3,10 @@
 thisdir=`dirname $0`
 basedir=`cd $thisdir/..; pwd`
 
-ulimit -n `ulimit -H -n`
+ulimit_max=`ulimit -H -n`
+if [ $ulimit_max != "unlimited" ]; then
+    ulimit -n $ulimit_max
+fi
 
 # set the classpath
 for i in $basedir/lib/*.jar $basedir/lib/*.zip $basedir/build/lib/*.jar; do