diff --git a/bin/zkEnv.sh b/bin/zkEnv.sh
index 40889874818..dc9dc531af2 100755
--- a/bin/zkEnv.sh
+++ b/bin/zkEnv.sh
@@ -136,8 +136,16 @@ export CLASSPATH
 
 # default heap for zookeeper server
 ZK_SERVER_HEAP="${ZK_SERVER_HEAP:-1000}"
-export SERVER_JVMFLAGS="-Xmx${ZK_SERVER_HEAP}m $SERVER_JVMFLAGS"
+if [[ $ZK_SERVER_HEAP =~ ^[1-9][0-9]*$ ]]; then
+  export SERVER_JVMFLAGS="-Xmx${ZK_SERVER_HEAP}m $SERVER_JVMFLAGS"
+else
+  export SERVER_JVMFLAGS="$ZK_SERVER_HEAP $SERVER_JVMFLAGS"
+fi
 
 # default heap for zookeeper client
 ZK_CLIENT_HEAP="${ZK_CLIENT_HEAP:-256}"
-export CLIENT_JVMFLAGS="-Xmx${ZK_CLIENT_HEAP}m $CLIENT_JVMFLAGS"
+if [[ $ZK_CLIENT_HEAP =~ ^[1-9][0-9]*$ ]]; then
+  export CLIENT_JVMFLAGS="-Xmx${ZK_CLIENT_HEAP}m $CLIENT_JVMFLAGS"
+else
+  export CLIENT_JVMFLAGS="$ZK_CLIENT_HEAP $CLIENT_JVMFLAGS"
+fi