diff --git a/include/mbedtls/x509_csr.h b/include/mbedtls/x509_csr.h
index 7a9c2e0..fe9843c 100644
--- a/include/mbedtls/x509_csr.h
+++ b/include/mbedtls/x509_csr.h
@@ -282,7 +282,7 @@
  *
  * \note            f_rng may be NULL if RSA is used for signature and the
  *                  signature is made offline (otherwise f_rng is desirable
- *                  for couermeasures against timing attacks).
+ *                  for countermeasures against timing attacks).
  *                  ECDSA signatures always require a non-NULL f_rng.
  */
 int mbedtls_x509write_csr_pem( mbedtls_x509write_csr *ctx, unsigned char *buf, size_t size,