Be extra anal with the bit types.
diff --git a/fatattr.c b/fatattr.c
index 9794909..83a27ad 100644
--- a/fatattr.c
+++ b/fatattr.c
@@ -120,7 +120,7 @@
       exit(EX_USAGE);
     }
 
-    attr |= 1 << (p-bit_to_char);
+    attr |= (uint32_t)1 << (p-bit_to_char);
     attrs++;
   }