diff --git a/cf/largefile.m4 b/cf/largefile.m4
index 5c54897be..cdbbc5543 100644
--- a/cf/largefile.m4
+++ b/cf/largefile.m4
@@ -10,7 +10,7 @@ dnl with generated code, such as lex
 if test "$enable_largefile" != no -a "$ac_cv_sys_large_files" != no; then
 	CPPFLAGS="$CPPFLAGS -D_LARGE_FILES=$ac_cv_sys_large_files"
 fi
-if test "$enable_largefile" != no -a "$ac_cv_sys_file_offset_bits" != no; then
+if test "$enable_largefile" != no -a "$ac_cv_sys_file_offset_bits" != no && test -n "$ac_cv_sys_file_offset_bits"; then
 	CPPFLAGS="$CPPFLAGS -D_FILE_OFFSET_BITS=$ac_cv_sys_file_offset_bits"
 fi
 ])