diff --git a/src/util.c b/src/util.c
index 08f3721..cb90f19 100644
--- a/src/util.c
+++ b/src/util.c
@@ -34,6 +34,45 @@
 #endif
 #endif
 
+#if defined(__linux__) && defined(__riscv)
+#if __has_include(<sys/hwprobe.h>)
+#include <sys/hwprobe.h>
+#else
+#include <unistd.h>
+
+#if __has_include(<asm/hwprobe.h>)
+#include <asm/hwprobe.h>
+#include <sys/syscall.h>
+#else
+#define __NR_riscv_hwprobe 258
+struct riscv_hwprobe {
+    int64_t key;
+    uint64_t value;
+};
+#define RISCV_HWPROBE_KEY_IMA_EXT_0 4
+#endif
+
+// RISC-V Scalar AES [E]ncryption and [D]ecryption
+#ifndef RISCV_HWPROBE_EXT_ZKND
+#define RISCV_HWPROBE_EXT_ZKND (1 << 11)
+#define RISCV_HWPROBE_EXT_ZKNE (1 << 12)
+#endif
+
+// RISC-V Vector AES
+#ifndef RISCV_HWPROBE_EXT_ZVKNED
+#define RISCV_HWPROBE_EXT_ZVKNED (1 << 21)
+#endif
+
+static int __riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
+                           size_t cpu_count, unsigned long *cpus,
+                           unsigned int flags)
+{
+    return syscall(__NR_riscv_hwprobe, pairs, pair_count, cpu_count, cpus, flags);
+}
+
+#endif
+#endif
+
 int write_bool(char *path, bool val) {
   int fd = open(path, O_RDWR);
 
@@ -90,10 +129,18 @@ bool has_fast_aes() {
   return __builtin_cpu_supports("aes");
 #elif defined(__BUILTIN_CPU_SUPPORTS__) && defined(__powerpc__)
   return __builtin_cpu_supports("vcrypto");
-#elif defined(__riscv)
-  // TODO: Implement detection of RISC-V vector crypto extension when possible.
-  // At the time of writing, no RISC-V hardware has it, so hardcode it off.
-  return false;
+#elif defined(__linux__) && defined(__riscv)
+    struct riscv_hwprobe pairs[1] = {
+        { RISCV_HWPROBE_KEY_IMA_EXT_0, 0 },
+    };
+
+    // If this syscall is not implemented, we'll get -ENOSYS
+    // and the value field will remain zero.
+    __riscv_hwprobe(pairs, sizeof(pairs) / sizeof(struct riscv_hwprobe), 0, NULL, 0);
+
+    return (pairs[0].value & (RISCV_HWPROBE_EXT_ZKNE | RISCV_HWPROBE_EXT_ZKND)) ==
+               (RISCV_HWPROBE_EXT_ZKNE | RISCV_HWPROBE_EXT_ZKND) ||
+           (pairs[0].value & RISCV_HWPROBE_EXT_ZVKNED);
 #elif __SIZEOF_SIZE_T__ == 4
   #warning Unknown 32-bit platform. Assuming AES is slow on this CPU.
   return false;