diff --git a/src/write.c b/src/write.c
index 5b66c31..d086b02 100644
--- a/src/write.c
+++ b/src/write.c
@@ -943,6 +943,7 @@
     }
 
     if (encoder->extraLayerCount >= AVIF_MAX_AV1_LAYER_COUNT) {
+        avifDiagnosticsPrintf(&encoder->diag, "extraLayerCount [%u] must be less than %d", encoder->extraLayerCount, AVIF_MAX_AV1_LAYER_COUNT);
         return AVIF_RESULT_INVALID_ARGUMENT;
     }