diff --git a/libsrc/atari/Makefile b/libsrc/atari/Makefile
index 7675be64d..a63efa831 100644
--- a/libsrc/atari/Makefile
+++ b/libsrc/atari/Makefile
@@ -1,8 +1,9 @@
 #
 # makefile for CC65 Atari runtime library
 #
+# NUMDRVS - number of supported drives (max. 16)
 
-ATARIDEFS =
+ATARIDEFS = -DNUMDRVS=4
 
 .SUFFIXES: .o .s .c
 
@@ -22,7 +23,7 @@ S_OBJS = crt0.o kbhit.o conio.o clrscr.o cputc.o ctype.o chline.o cvline.o \
 	 gotox.o gotoy.o savevec.o rwcommon.o cgetc.o read.o getargs.o close.o \
 	 open.o oserror.o fdtable.o setcolor.o scroll.o mul40.o graphuse.o \
 	 ostype.o clock.o lseek.o dioread.o diowrite.o siocall.o diowritev.o \
-	 dio_cts.o dio_stc.o
+	 dio_cts.o dio_stc.o diopncls.o
 
 all:	$(C_OBJS) $(S_OBJS)