diff --git a/platform/c64/Makefile.c64 b/platform/c64/Makefile.c64
index d3c819f67..fb567e1bc 100644
--- a/platform/c64/Makefile.c64
+++ b/platform/c64/Makefile.c64
@@ -1,2 +1,5 @@
+CFLAGS += -DWITH_PETSCII
+CONTIKI_TARGET_SOURCEFILES += petsciiconv.c
+
 CONTIKI_CPU = $(CONTIKI)/cpu/6502
 include $(CONTIKI_CPU)/Makefile.6502