diff --git a/pack-initrd b/pack-initrd
index adda676..0c5f33a 100755
--- a/pack-initrd
+++ b/pack-initrd
@@ -4,5 +4,15 @@
 initrd=${1:-initrd.img}
 ramdisk=${2:-ramdisk}
 
+if [ ! -d $ramdisk ]; then
+    echo "$ramdisk does not exist."
+    exit 1
+fi
+
+if [ -f $initrd ]; then
+    echo "$initrd already exist."
+    exit 1
+fi
+
 ( cd $ramdisk; find | sort | cpio --quiet -o -H newc ) | gzip > $initrd
 
diff --git a/unpack-initrd b/unpack-initrd
index 6530f12..987239c 100755
--- a/unpack-initrd
+++ b/unpack-initrd
@@ -4,6 +4,11 @@
 initrd=${1:-initrd.img}
 ramdisk=${2:-ramdisk}
 
+if [ ! -f $initrd ]; then
+    echo "$initrd does not exist."
+    exit 1
+fi
+
 if [ -d $ramdisk ]; then
     echo "$ramdisk already exists."
     exit 1