diff --git a/scst/include/scst.h b/scst/include/scst.h
index b158338ab..cd8272635 100644
--- a/scst/include/scst.h
+++ b/scst/include/scst.h
@@ -39,6 +39,22 @@
 #include <scsi/scsi_eh.h>
 #include <scsi/scsi.h>
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 33)
+/*
+ * From <scsi/scsi.h>. See also commit
+ * f57e4502cea471c69782d4790c71d8414ab49a9d.
+ */
+#define UNMAP 0x42
+#endif
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 27)
+/*
+ * From <linux/fs.h>. See also commit
+ * d30a2605be9d5132d95944916e8f578fcfe4f976.
+ */
+#define BLKDISCARD _IO(0x12,119)
+#endif
+
 #ifdef INSIDE_KERNEL_TREE
 #include <scst/scst_const.h>
 #else