diff --git a/src/ipv4.c b/src/ipv4.c
index 698bf108..46bfda6d 100644
--- a/src/ipv4.c
+++ b/src/ipv4.c
@@ -232,6 +232,7 @@ static int ipv4_get_route(struct rtentry *route)
 	while (fgets(line, buffer_size - total_bytes_read - 1, fp) != NULL) {
 		uint32_t bytes_read = strlen(line);
 
+		assert(total_bytes_read < UINT32_MAX - bytes_read);
 		total_bytes_read += bytes_read;
 
 		if (bytes_read > 0 && line[bytes_read - 1] != '\n') {