1 files changed, 4 insertions, 1 deletions
diff --git a/vui.c b/vui.c
index 8c4a58a..379fdb9 100644
--- a/vui.c
+++ b/vui.c
@@ -584,6 +584,7 @@ end:
 }
 
 void vui_chra(int x, int y, VuiChar c, VuiAttr a) {
+	ASSERT(c > 0 && c <= KEY_UTF8_MAX);
 	if (x >= 0 && x < (int)COLS && y >= 0 && y < (int)LINES) {
 		CHR(x, y) = c;
 		ATTR(x, y) = a;
@@ -617,7 +618,9 @@ void vui_putsna(int x, int y, const char *s, unsigned srcn, VuiAttr a) {
 	u32 n = utf8_decode_len(s, srcn);
 	truncate_span(&x, &n);
 	if (n < 1 || y < 0 || y >= (int)LINES) return;
-	utf8_decode(&CHR(x, y), s, n);
+	VuiChar *dest = &CHR(x, y);
+	utf8_decode(dest, s, n);
+	for (u32 i = 0; i < n; i++) ASSERT(dest[i] > 0 && dest[i] <= KEY_UTF8_MAX);
 	for (uint16_t *pa = &ATTR(x, y); n--;) *pa++ = a;
 }