diff --git a/library/pk_internal.h b/library/pk_internal.h
index 402cb65..09f3d85 100644
--- a/library/pk_internal.h
+++ b/library/pk_internal.h
@@ -63,6 +63,26 @@
             return NULL;
     }
 }
+
+/* Helpers for Montgomery curves */
+#if defined(MBEDTLS_ECP_DP_CURVE25519_ENABLED) || defined(MBEDTLS_ECP_DP_CURVE448_ENABLED)
+#define MBEDTLS_PK_HAVE_RFC8410_CURVES
+
+static inline int mbedtls_pk_is_rfc8410_curve(mbedtls_ecp_group_id id)
+{
+#if defined(MBEDTLS_ECP_DP_CURVE25519_ENABLED)
+    if (id == MBEDTLS_ECP_DP_CURVE25519) {
+        return 1;
+    }
+#endif
+#if defined(MBEDTLS_ECP_DP_CURVE448_ENABLED)
+    if (id == MBEDTLS_ECP_DP_CURVE448) {
+        return 1;
+    }
+#endif
+    return 0;
+}
+#endif /* MBEDTLS_ECP_DP_CURVE25519_ENABLED || MBEDTLS_ECP_DP_CURVE448_ENABLED */
 #endif /* MBEDTLS_ECP_LIGHT */
 
 #endif /* MBEDTLS_PK_INTERNAL_H */