diff --git a/preload.sh b/preload.sh
index 40d13f5..f6b155e 100755
--- a/preload.sh
+++ b/preload.sh
@@ -1,5 +1,6 @@
 #!/bin/bash
 
-dir=$(cd "$(dirname ${BASH_SOURCE[0]})" && pwd)
-export LD_PRELOAD+=" $dir/hardened_malloc.so"
-exec $@
+dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+[[ $LD_PRELOAD ]] && LD_PRELOAD+=" "
+export LD_PRELOAD+="$dir/hardened_malloc.so"
+exec "$@"