diff --git a/regexp.py b/regexp.py
--- a/regexp.py
+++ b/regexp.py
@@ -1,6 +1,10 @@
 from abc import abstractmethod
 
 
+class ParsingError(Exception):
+	pass
+
+
 class Token:
 	is_skippable = False
 
@@ -111,7 +115,7 @@ def find_closing_parenthesis(pattern, k)
 		if counter == 0:
 			return k+i
 
-	return None
+	raise ParsingError(f'A closing parenthesis not found. Pattern: "{pattern}", position: {k}')
 
 
 def parse(pattern, offset=0):
@@ -126,13 +130,21 @@ def parse(pattern, offset=0):
 			res.append(inner_content)
 			i = j+1
 		elif c == "*":
-			token = res.pop()
+			try:
+				token = res.pop()
+			except IndexError as e:
+				raise ParsingError(f'The asterisk operator is missing an argument. Pattern: "{pattern}", position {i}')
 			res.append(Asterisk(token))
 			i += 1
 		elif c == "+":
-			token = res.pop()
+			try:
+				token = res.pop()
+			except IndexError as e:
+				raise ParsingError(f'The plus operator is missing an argument. Pattern: "{pattern}", position {i}')
 			res.append(Plus(token))
 			i += 1
+		elif c == ")":
+			raise ParsingError(f'An opening parenthesis not found. Pattern: "{pattern}", position: {i}')
 		else:
 			res.append(Symbol(i+offset, c))
 			i += 1
@@ -228,9 +240,14 @@ class RegexpDFA:
 
 if __name__ == "__main__":
 	tests = ["", "a", "ab", "aabb", "abab", "abcd", "abcbcdbcd"]
-	for pattern in ["a*b*", "a+b+", "(ab)*", "(ab)+", "a((bc)*d)*"]:
+	for pattern in ["*", "((a)", "a)"]:
 		print("#", pattern)
-		r = RegexpDFA(pattern)
+		try:
+			r = RegexpDFA(pattern)
+		except ParsingError as e:
+			print("Failed to parse the regexp:")
+			print(e)
+			continue
 		for t in tests:
 			print(t, r.match(t))
 		print()