diff --git a/bacnet-stack/ports/atmega168/Makefile b/bacnet-stack/ports/atmega168/Makefile
index 508ebdd6..898e3c93 100644
--- a/bacnet-stack/ports/atmega168/Makefile
+++ b/bacnet-stack/ports/atmega168/Makefile
@@ -97,7 +97,7 @@ OPTIMIZATION = -Os $(OPTIMIZE_FLAGS)
 
 ## Compile options common for all C compilation units.
 BFLAGS = -DBACDL_MSTP
-BFLAGS += -DMAX_APDU=128
+BFLAGS += -DMAX_APDU=50
 BFLAGS += -DBIG_ENDIAN=0
 BFLAGS += -DMAX_TSM_TRANSACTIONS=0
 #BFLAGS += -DCRC_USE_TABLE