diff --git a/src/lorawan.cpp b/src/lorawan.cpp
index bc8565de..edc0d630 100644
--- a/src/lorawan.cpp
+++ b/src/lorawan.cpp
@@ -6,6 +6,10 @@ static const char TAG[] = "lora";
 
 #ifdef HAS_LORA
 
+#if CLOCK_ERROR_PROCENTAGE > 7 
+#warning CLOCK_ERROR_PROCENTAGE value in lmic_config.h is too high; values > 7 will cause side effects
+#endif
+
 osjob_t sendjob;
 QueueHandle_t LoraSendQueue;