diff --git a/asm/creole.py b/asm/creole.py
index e323432..d8f5d32 100644
--- a/asm/creole.py
+++ b/asm/creole.py
@@ -338,13 +338,18 @@ class Line:
 		self.ins = ins
 		self.args = args
 
-	def check_line(self, lablen, reglen):
+	def check_line(self, reglen, datlen):
 		for a in self.args:
 			if a.at == ArgType.REG:
 				if a.val < 0 or a.val >= reglen:
 					raise RangeCheckException(a.at,
 					                          a.val,
 					                          reglen)
+			elif a.at == ArgType.DAT:
+				if a.val < 0 or a.val >= datlen:
+					raise RangeCheckException(a.at,
+					                          a.val,
+					                          reglen)
 	def __call__(self):
 		return self.ins.render(self.args)
 
@@ -366,7 +371,7 @@ def _term_sep(s):
 class Program:
 	def _asm_push_line(self, ins, args):
 		l = Line(ins, args)
-		l.check_line(self.lablen, self.reglen)
+		l.check_line(self.reglen, self.datlen)
 		self.asm.append(l)
 
 	def parse_asm_line(self, line):
@@ -454,8 +459,8 @@ class Program:
 		assert len(b) < encoding_types[lablen][0]
 		return b
 
-	def __init__(self, lablen=16, reglen=16):
+	def __init__(self, reglen=16, datlen=16):
 		self.asm = []
-		self.lablen = lablen
 		self.reglen = reglen
+		self.datlen = datlen