diff --git a/firmware/Makefile b/firmware/Makefile
index 730ea66..875e034 100644
--- a/firmware/Makefile
+++ b/firmware/Makefile
@@ -7,7 +7,7 @@
 LFUSE = D2
 HFUSE = 91
 EFUSE = FF
-F_CPU = 20000000
+F_CPU = 8000000
 DEBUG = -DB15F_DEBUG
 
 # Environment