diff --git a/include/sys/sunldi.h b/include/sys/sunldi.h
index 43462efad..a5045f891 100644
--- a/include/sys/sunldi.h
+++ b/include/sys/sunldi.h
@@ -32,6 +32,12 @@
 #include <linux/bio.h>
 #include <linux/blkdev.h>
 
+/*
+ * SECTOR_SIZE can be defined in blkdev.h. See
+ * https://github.com/torvalds/linux/commit/233bde21.
+ */
+#ifndef SECTOR_SIZE
 #define	SECTOR_SIZE 512
+#endif
 
 #endif /* SPL_SUNLDI_H */