diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index ebe4a2593c40..16488b33f238 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -473,7 +473,8 @@ static const unsigned int riscv_c_exts[] = {
 
 /*
  * The canonical order of ISA extension names in the ISA string is defined in
- * chapter 27 of the unprivileged specification.
+ * Chapter 27 of the RISC-V Instruction Set Manual Volume I Unprivileged ISA
+ * (Document Version 20191213).
  *
  * Ordinarily, for in-kernel data structures, this order is unimportant but
  * isa_ext_arr defines the order of the ISA string in /proc/cpuinfo.