diff --git a/ethertype-dump.c b/ethertype-dump.c
index 0c6cd0d..b999184 100644
--- a/ethertype-dump.c
+++ b/ethertype-dump.c
@@ -39,7 +39,7 @@ int main(void) {
 	}
 
 	for(;;) {
-		char frame[1522]; // 1522 is the largest a 802.3 frame can be
+		unsigned char frame[1522]; // 1522 is the largest a 802.3 frame can be
 
 		errno = 0;
 		ssize_t frame_length = recv(packet_socket, frame, sizeof(frame), MSG_TRUNC);