diff --git a/config.mk b/config.mk
index 373e20d..9fb18da 100644
--- a/config.mk
+++ b/config.mk
@@ -10,8 +10,7 @@ AR = ar
 RANLIB = ranlib
 
 # for NetBSD add -D_NETBSD_SOURCE
-# for glibc on 32bit add -D_FILE_OFFSET_BITS=64 or use something sane
 # -lrt might be needed on some systems
-CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700
+CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700 -D_FILE_OFFSET_BITS=64
 CFLAGS   = -std=c99 -Wall -pedantic
 LDFLAGS  = -s