diff --git a/parser.py b/parser.py
index ba292cb..b1fdc23 100644
--- a/parser.py
+++ b/parser.py
@@ -112,7 +112,7 @@ class LLVMParser(object):
         self.current_string += '\\'
 
     def t_string_hex(self, t):
-        r'\\[0-9a-f][0-9a-f]'
+        r'\\[0-9a-fA-F][0-9a-fA-F]'
         code = int(t.value[1:], 16)
         self.current_string += chr(code)