--- thirdparty_unman/chmlib/configure.in.orig
+++ thirdparty_unman/chmlib/configure.in
@@ -97,7 +97,7 @@ AC_ARG_ENABLE(dmalloc,
 
 dnl check for availability of the functions we need
 if test -n "$CHM_USE_IO64"; then
-    AC_CHECK_FUNC(lseek64,,[
+    AC_CHECK_FUNC(lseek,,[
             AC_MSG_WARN([64-bit file offsets not available, huge files won't be supported.])
             CHM_USE_IO64=""])
 fi