diff --git a/armsrc/BigBuf.c b/armsrc/BigBuf.c
index 5f1ace5f8..8ee7cc189 100644
--- a/armsrc/BigBuf.c
+++ b/armsrc/BigBuf.c
@@ -156,8 +156,8 @@ bool RAMFUNC LogTrace(const uint8_t *btBytes, uint16_t iLen, uint32_t timestamp_
         tracing = false; // don't trace any more
         return false;
     }
-    if (timestamp_end - timestamp_start > UINT16_MAX) {
-        return false; // duration too long
+    if (timestamp_end - timestamp_start > 0x7FFF) {
+        return false; // duration too long, must be max 15 bits
     }
     hdr->timestamp = timestamp_start;
     hdr->duration = timestamp_end - timestamp_start;