diff --git a/watch.c b/watch.c
index 1e050dc6..af7d2620 100644
--- a/watch.c
+++ b/watch.c
@@ -296,9 +296,9 @@ main(int argc, char *argv[])
 				move(y, x);
 				if (option_differences) {
 					chtype oldch = inch();
-					char oldc = oldch & A_CHARTEXT;
+					unsigned char oldc = oldch & A_CHARTEXT;
 					attr = !first_screen
-					    && ((char)c != oldc
+					    && ((unsigned char)c != oldc
 						||
 						(option_differences_cumulative
 						 && (oldch & A_ATTRIBUTES)));