diff --git a/src/capdiff.c b/src/capdiff.c
index 87a4b67..5ab055c 100644
--- a/src/capdiff.c
+++ b/src/capdiff.c
@@ -68,7 +68,7 @@ int main(int argc, char** argv) {
 
 
     size_t max_size = s1 > s2 ? s1 : s2;
-    for (size_t idx = 0; idx < max_size; idx++) {
+    for (size_t idx = sizeof(bpread[0].ip.ap.fmt.headers) + sizeof(bpread[0].ip.ap.fmt.content.clear) - sizeof(char); idx < max_size; idx++) {
       char e1 = (&bpread[0].ip.ap.raw)[idx], e2 = (&bpread[1].ip.ap.raw)[idx];
       if (e1 != e2) {
         printf("[!!] for expected id %d, byte 0x%04x is different: 0x%02x vs 0x%02x\n", expected_id, (uint16_t)idx, (uint8_t)e1, (uint8_t)e2);