diff --git a/dump.c b/dump.c
index 94e4796..ba5fa3e 100644
--- a/dump.c
+++ b/dump.c
@@ -220,6 +220,7 @@
   char output[PACKETLEN*3+2];
   size_t i;
 
+  output[0] = '\0';
   for(i = 0; i < len && i < PACKETLEN; i++) {
     snprintf(output + i*3, 4, " %02x", (uint8_t)data[i]);
   }