diff --git a/lib/sbi/sbi_scratch.c b/lib/sbi/sbi_scratch.c
index bb14a1a2..21120b14 100644
--- a/lib/sbi/sbi_scratch.c
+++ b/lib/sbi/sbi_scratch.c
@@ -21,7 +21,8 @@ u32 hartindex_to_hartid_table[SBI_HARTMASK_MAX_BITS] = { [0 ... SBI_HARTMASK_MAX
 struct sbi_scratch *hartindex_to_scratch_table[SBI_HARTMASK_MAX_BITS];
 
 static spinlock_t extra_lock = SPIN_LOCK_INITIALIZER;
-static unsigned long extra_offset = SBI_SCRATCH_EXTRA_SPACE_OFFSET;
+static unsigned long
+	extra_offset GUARDED_BY(&extra_lock) = SBI_SCRATCH_EXTRA_SPACE_OFFSET;
 
 /*
  * Get the alignment size.