diff --git a/lib/sbi_hart.c b/lib/sbi_hart.c
index 5b26aead..a375ecf6 100644
--- a/lib/sbi_hart.c
+++ b/lib/sbi_hart.c
@@ -203,6 +203,10 @@ void __attribute__((noreturn)) sbi_hart_boot_next(unsigned long arg0,
 
 	if (next_mode != PRV_S && next_mode != PRV_M && next_mode != PRV_U)
 		sbi_hart_hang();
+	if (next_mode == PRV_S && !misa_extension('S'))
+		sbi_hart_hang();
+	if (next_mode == PRV_U && !misa_extension('U'))
+		sbi_hart_hang();
 
 	val = csr_read(mstatus);
 	val = INSERT_FIELD(val, MSTATUS_MPP, next_mode);