diff --git a/src/mares_nemo.c b/src/mares_nemo.c
index eb2cbcb..40c25dc 100644
--- a/src/mares_nemo.c
+++ b/src/mares_nemo.c
@@ -35,6 +35,10 @@
 	rc == -1 ? DEVICE_STATUS_IO : DEVICE_STATUS_TIMEOUT \
 )
 
+#ifdef PACKETSIZE
+#undef PACKETSIZE /* Override the common value. */
+#endif
+
 #define MEMORYSIZE 0x4000
 #define PACKETSIZE 0x20