diff --git a/src/rcfile.c b/src/rcfile.c
index 0f324ea0..683d88d2 100644
--- a/src/rcfile.c
+++ b/src/rcfile.c
@@ -756,10 +756,11 @@ void parse_binding(char *ptr, bool dobind)
 	keycopy = copy_of(keyptr);
 
 	/* Uppercase either the second or the first character of the key name. */
-	if (keycopy[0] == '^')
-		keycopy[1] = toupper((unsigned char)keycopy[1]);
-	else
-		keycopy[0] = toupper((unsigned char)keycopy[0]);
+	if (keycopy[0] == '^') {
+		if ('a' <= keycopy[1] && keycopy[1] <= 'z')
+			keycopy[1] &= 0x5F;
+	} else if ('a' <= keycopy[0] && keycopy[0] <= 'z')
+		keycopy[0] &= 0x5F;
 
 	/* Verify that the key name is not too short. */
 	if (keycopy[1] == '\0' || (keycopy[0] == 'M' && keycopy[2] == '\0')) {
diff --git a/src/winio.c b/src/winio.c
index bb56e771..3f05dc11 100644
--- a/src/winio.c
+++ b/src/winio.c
@@ -1046,8 +1046,8 @@ int parse_kbinput(WINDOW *frame)
 				meta_key = TRUE;
 		} else if (waiting_codes == 0 || nextcodes[0] == ESC_CODE ||
 								(keycode != 'O' && keycode != '[')) {
-			if (!shifted_metas)
-				keycode = tolower(keycode);
+			if ('A' <= keycode && keycode <= 'Z' && !shifted_metas)
+				keycode |= 0x20;
 			meta_key = TRUE;
 		} else
 			keycode = parse_escape_sequence(keycode);
@@ -1105,8 +1105,8 @@ int parse_kbinput(WINDOW *frame)
 			/* If the first escape arrived alone but not the second, then it
 			 * is a Meta keystroke; otherwise, it is an "Esc Esc control". */
 			if (first_escape_was_alone && !last_escape_was_alone) {
-				if (!shifted_metas)
-					keycode = tolower(keycode);
+				if ('A' <= keycode && keycode <= 'Z' && !shifted_metas)
+					keycode |= 0x20;
 				meta_key = TRUE;
 			} else
 				keycode = convert_to_control(keycode);