diff --git a/include/mbedtls/x509_internal.h b/include/mbedtls/x509_internal.h
index 3816c3611..bed9772e3 100644
--- a/include/mbedtls/x509_internal.h
+++ b/include/mbedtls/x509_internal.h
@@ -89,7 +89,7 @@ int mbedtls_x509_name_cmp_raw( mbedtls_x509_buf_raw const *a,
                                              int next_merged ),
                                void *check_ctx );
 int mbedtls_x509_memcasecmp( const void *s1, const void *s2,
-                             size_t len1, size_t lend2 );
+                             size_t len1, size_t len2 );
 int mbedtls_x509_get_ext( unsigned char **p, const unsigned char *end,
                   mbedtls_x509_buf *ext, int tag );