diff --git a/lib/raop_ntp.c b/lib/raop_ntp.c
index 0431506..92eec49 100644
--- a/lib/raop_ntp.c
+++ b/lib/raop_ntp.c
@@ -290,10 +290,10 @@ raop_ntp_thread(void *arg)
         byteutils_put_ntp_timestamp(request, 24, send_time);
         int send_len = sendto(raop_ntp->tsock, (char *)request, sizeof(request), 0,
                               (struct sockaddr *) &raop_ntp->remote_saddr, raop_ntp->remote_saddr_len);
-	if (logger_debug) {
-            char *str = utils_data_to_string(request, send_len, 16);
-            logger_log(raop_ntp->logger, LOGGER_DEBUG, "\nraop_ntp send time type_t=%d send_len = %d, now = %8.6f\n%s",
-                       request[1] &~0x80, send_len, (double) send_time / SECOND_IN_NSECS, str);
+        if (logger_debug) {
+            char *str = utils_data_to_string(request, sizeof(request), 16);
+            logger_log(raop_ntp->logger, LOGGER_DEBUG, "\nraop_ntp send time type_t=%d packetlen = %d, now = %8.6f\n%s",
+                       request[1] &~0x80, sizeof(request), (double) send_time / SECOND_IN_NSECS, str);
             free(str);
         }
         if (send_len < 0) {
diff --git a/lib/utils.c b/lib/utils.c
index 07788ec..8ad59c4 100644
--- a/lib/utils.c
+++ b/lib/utils.c
@@ -187,7 +187,12 @@ char *utils_parse_hex(const char *str, int str_len, int *data_len) {
 }
 
 char *utils_data_to_string(const unsigned char *data, int datalen, int chars_per_line) {
-    int len = 3*datalen + ((datalen-1)/chars_per_line ) + 1;
+    assert(datalen >= 0);
+    assert(chars_per_line > 0);
+    int len = 3*datalen + 1;
+    if (datalen > chars_per_line) {
+        len += (datalen-1)/chars_per_line;
+    }
     char *str = (char *) calloc(len + 1, sizeof(char));
     assert(str);
     char *p = str;