diff --git a/BasiliskII/src/Unix/configure.in b/BasiliskII/src/Unix/configure.in
index 899dff92..eea12ff7 100644
--- a/BasiliskII/src/Unix/configure.in
+++ b/BasiliskII/src/Unix/configure.in
@@ -5,10 +5,6 @@ AC_INIT(main_unix.cpp)
 AC_PREREQ(2.12)
 AC_CONFIG_HEADER(config.h)
 
-dnl These defines are necessary to get 64-bit file size support.
-AC_DEFINE(_USE_LARGEFILE_SOURCE, 1, [Get more functions for correct standard I/O])
-AC_DEFINE(_FILE_OFFSET_BITS, 64, [Get 64-bit file size support])
-
 dnl Options.
 AC_ARG_ENABLE(xf86-dga,      [  --enable-xf86-dga       use the XFree86 DGA extension [default=yes]], [WANT_XF86_DGA=$enableval], [WANT_XF86_DGA=yes])
 AC_ARG_ENABLE(xf86-vidmode,  [  --enable-xf86-vidmode   use the XFree86 VidMode extension [default=yes]], [WANT_XF86_VIDMODE=$enableval], [WANT_XF86_VIDMODE=yes])
@@ -201,6 +197,13 @@ if [[ "x$WANT_ESD" = "xyes" ]]; then
   ])
 fi
 
+dnl We use 64-bit file size support if possible.
+dnl FIXME: Use AC_SYS_LARGEFILE from autoconf 2.5+
+if [[ "x$OS_TYPE" = "xlinux" ]]; then
+  AC_DEFINE(_USE_LARGEFILE_SOURCE, 1, [Get more functions for correct standard I/O])
+  AC_DEFINE(_FILE_OFFSET_BITS, 64, [Get 64-bit file size support])
+fi
+
 dnl Checks for header files.
 AC_HEADER_STDC
 AC_CHECK_HEADERS(unistd.h fcntl.h sys/time.h sys/mman.h)