diff --git a/plugins/SedRegex/plugin.py b/plugins/SedRegex/plugin.py
index 61c8a712f..233429b17 100644
--- a/plugins/SedRegex/plugin.py
+++ b/plugins/SedRegex/plugin.py
@@ -53,8 +53,7 @@ if sys.version_info[0] < 3:
                       'https://github.com/jlu5/SupyPlugins/tree/python2-legacy')
 
 SED_REGEX = re.compile(r"^(?:(?P<nick>.+?)[:,] )?s(?P<delim>[^\w\s])(?P<pattern>.*?)(?P=delim)"
-                       r"(?P<replacement>.*?)(?P=delim)(?P<flags>[a-z]*)$",
-                       re.I)
+                       r"(?P<replacement>.*?)(?P=delim)(?P<flags>[a-z]*)$")
 
 # Replace newlines and friends with things like literal "\n" (backslash and "n")
 axe_spaces = utils.str.MultipleReplacer({'\n': '\\n', '\t': '\\t', '\r': '\\r'})
@@ -86,12 +85,15 @@ class SedRegex(callbacks.PluginRegexp):
 
         match = SED_REGEX.search(escaped_expr)
 
+        if not match:
+            return
+
         groups = match.groupdict()
         pattern = groups['pattern'].replace('\0', delim)
         replacement = groups['replacement'].replace('\0', delim)
 
         if groups['flags']:
-            raw_flags = set(groups['flags'].lower())
+            raw_flags = set(groups['flags'])
         else:
             raw_flags = set()
 
diff --git a/plugins/SedRegex/test.py b/plugins/SedRegex/test.py
index 7ee842138..50a045ca5 100644
--- a/plugins/SedRegex/test.py
+++ b/plugins/SedRegex/test.py
@@ -51,12 +51,6 @@ class SedRegexTestCase(ChannelPluginTestCase):
         m = self.getMsg(' ')
         self.assertIn('Abcd testefgh', str(m))
 
-    def testCaseInsensitiveRegexp(self):
-        self.feedMsg('aliens are invading, help!')
-        self.feedMsg('S/a/e/i')
-        m = self.getMsg(' ')
-        self.assertIn('eliens', str(m))
-
     def testCaseInsensitiveReplace(self):
         self.feedMsg('Aliens Are Invading, Help!')
         self.feedMsg('s/a/e/i')