diff --git a/migScope/tools/truthtable.py b/migScope/tools/truthtable.py
index d38316b9d..14ce7969e 100644
--- a/migScope/tools/truthtable.py
+++ b/migScope/tools/truthtable.py
@@ -2,14 +2,26 @@ import os
 import re 
 import sys
 
+def is_number(x):
+    try:
+        _ = float(x)
+    except ValueError:
+        return False
+    return True
+
+def remove_numbers(seq):
+	return [ x for x in seq if not is_number(x)]
+
 def remove_duplicates(seq):
-    seen = set()
-    seen_add = seen.add
-    return [ x for x in seq if x not in seen and not seen_add(x)]
+	seen = set()
+	seen_add = seen.add
+	return [ x for x in seq if x not in seen and not seen_add(x)]
 
 def get_operands(s):
-	operands = remove_duplicates(sorted(re.findall("[A-z0-9_]+", s)))
-	return operands
+	operands = re.findall("[A-z0-9_]+", s)
+	operands = remove_duplicates(operands)
+	operands = remove_numbers(operands)
+	return sorted(operands)
 
 def gen_truth_table(s):
 	operands = get_operands(s)
@@ -30,6 +42,6 @@ def gen_truth_table(s):
 
 def main():
 	print(gen_truth_table("(A&B&C)|D"))
-
+	
 if __name__ == '__main__':
-  main()
+	main()