diff --git a/Modules/_sre.c b/Modules/_sre.c
index baf5f6a..a5a6b1e 100644
--- a/Modules/_sre.c
+++ b/Modules/_sre.c
@@ -459,7 +459,7 @@
             }
             else {
                 /* <CHARSET> <bitmap> (32 bits per code word) */
-                if (ch < 256 && (set[ch >> 5] & (1 << (ch & 31))))
+                if (ch < 256 && (set[ch >> 5] & (1u << (ch & 31))))
                     return ok;
                 set += 8;
             }
@@ -498,7 +498,7 @@
                     block = -1;
                 set += 64;
                 if (block >=0 &&
-                    (set[block*8 + ((ch & 255)>>5)] & (1 << (ch & 31))))
+                    (set[block*8 + ((ch & 255)>>5)] & (1u << (ch & 31))))
                     return ok;
                 set += count*8;
             }