diff --git a/README.md b/README.md
index 01c56a0..ab9fa21 100644
--- a/README.md
+++ b/README.md
@@ -57,7 +57,7 @@ options:
   -w, --width        image width (default: 1920)
   -h, --height       image height (default: 1080)
   -o, --output       output file (default: output.bmp)
-  -seed              random seed (default: time based)
+  --seed             random seed (default: time based)
   -p, --pixel        pixel size (default: random)
   -s, --slope        slope [0-255] (default: random)
   -c, --color        base color [0-255,0-255,0-255] (default: random)
diff --git a/src/args.c b/src/args.c
index 31d12c6..f6885e4 100644
--- a/src/args.c
+++ b/src/args.c
@@ -32,7 +32,7 @@ void print_help(int status_code) {
        "  -w, --width        image width (default: 1920)\n"
        "  -h, --height       image height (default: 1080)\n"
        "  -o, --output       output file (default: output.bmp)\n"
-       "  -seed              random seed (default: time based)\n"
+       "  --seed             random seed (default: time based)\n"
        "  -p, --pixel        pixel size (default: random)\n"
        "  -s, --slope        slope [0-255] (default: random)\n"
        "  -c, --color        base color [0-255,0-255,0-255] (default: random)\n"
@@ -99,7 +99,7 @@ unsigned short parse_ushort(char *arg, char *value) {
   return (unsigned short)tmp_value;
 }
 
-unsigned short parse_ulong(char *arg, char *value) {
+unsigned long parse_ulong(char *arg, char *value) {
   if (!is_number(value)) {
     invalid_value(arg, value);
   }