diff -r a7bf938bc1e3 Lib/test/test_re.py
--- a/Lib/test/test_re.py	Thu Mar 20 11:28:16 2014 -0500
+++ b/Lib/test/test_re.py	Thu Mar 20 22:25:10 2014 +0200
@@ -1223,6 +1223,11 @@
             pat.scanner(string='abracadabra', pos=3, endpos=10).search().span(),
             (7, 9))
 
+    def test_bug_20998(self):
+        # Issue #20998: Fullmatch of repeated single character pattern
+        # with ignore case.
+        self.assertEqual(re.fullmatch('[a-c]+$', 'abc', re.I).span(), (0, 3))
+
 
 class PatternReprTests(unittest.TestCase):
     def check(self, pattern, expected):
diff -r a7bf938bc1e3 Modules/sre_lib.h
--- a/Modules/sre_lib.h	Thu Mar 20 11:28:16 2014 -0500
+++ b/Modules/sre_lib.h	Thu Mar 20 22:25:10 2014 +0200
@@ -259,7 +259,10 @@
         /* repeated single character pattern */
         TRACE(("|%p|%p|COUNT SUBPATTERN\n", pattern, ptr));
         while ((SRE_CHAR*) state->ptr < end) {
+            int match_all = state->match_all;
+            state->match_all = 0;
             i = SRE(match)(state, pattern);
+            state->match_all = match_all;
             if (i < 0)
                 return i;
             if (!i)