diff --git a/xpcom/idl-parser/xpidl/xpidl.py b/xpcom/idl-parser/xpidl/xpidl.py
index dd410999e0..44532351fe 100755
--- a/xpcom/idl-parser/xpidl/xpidl.py
+++ b/xpcom/idl-parser/xpidl/xpidl.py
@@ -1633,13 +1633,13 @@ class IDLParser(object):
     t_ignore = " \t"
 
     def t_multilinecomment(self, t):
-        r"/\*(?s).*?\*/"
+        r"/\*(?s:.)*?\*/"
         t.lexer.lineno += t.value.count("\n")
         if t.value.startswith("/**"):
             self._doccomments.append(t.value)
 
     def t_singlelinecomment(self, t):
-        r"(?m)//.*?$"
+        r"(?m://.*?$)"
 
     def t_IID(self, t):
         return t
@@ -1652,7 +1652,7 @@ class IDLParser(object):
         return t
 
     def t_LCDATA(self, t):
-        r"(?s)%\{[ ]*C\+\+[ ]*\n(?P<cdata>.*?\n?)%\}[ ]*(C\+\+)?"
+        r"(?s:%\{[ ]*C\+\+[ ]*\n(?P<cdata>.*?\n?)%\}[ ]*(C\+\+)?)"
         t.type = "CDATA"
         t.value = t.lexer.lexmatch.group("cdata")
         t.lexer.lineno += t.value.count("\n")