diff --git a/mmgen/config.py b/mmgen/config.py
index 051d1799..df64864c 100755
--- a/mmgen/config.py
+++ b/mmgen/config.py
@@ -40,9 +40,10 @@ hash_preset = '3'
 hash_presets = {
 #   Scrypt params:
 #   ID    N      p  r
-	'1': [2**12, 8, 1],
-	'2': [2**13, 8, 4],
-	'3': [2**14, 8, 8],
-	'4': [2**15, 8, 12],
-	'5': [2**16, 8, 16],
+# N is a power of two
+	'1': [12, 8, 1],
+	'2': [13, 8, 4],
+	'3': [14, 8, 8],
+	'4': [15, 8, 12],
+	'5': [16, 8, 16],
 }
diff --git a/mmgen/utils.py b/mmgen/utils.py
index 478928d2..4ce2c3d2 100755
--- a/mmgen/utils.py
+++ b/mmgen/utils.py
@@ -65,7 +65,7 @@ def show_hash_presets():
 	msg(fs.format("Preset","N","r","p"))
 	for i in sorted(hash_presets.keys()):
 		msg(fs.format("'%s'" % i, *hash_presets[i]))
-	msg("N = memory usage, p = iterations (rounds)")
+	msg("N = memory usage (power of two), p = iterations (rounds)")
 	sys.exit(0)
 
 
@@ -302,7 +302,7 @@ def _scrypt_hash_passphrase(passwd, salt, hash_preset, buflen=32):
 	N,r,p = _get_hash_params(hash_preset)
 
   	import scrypt
-	return scrypt.hash(passwd, salt, N, r, p, buflen=buflen)
+	return scrypt.hash(passwd, salt, 2**N, r, p, buflen=buflen)
 
 
 def _get_seed_from_brain_passphrase(words,opts):