diff --git a/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h b/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h
index 0574ba3e0..58cfcee9f 100644
--- a/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h
+++ b/embed/extmod/modtrezorcrypto/modtrezorcrypto-bip32.h
@@ -31,6 +31,7 @@ typedef struct _mp_obj_HDNode_t {
     mp_obj_base_t base;
     uint32_t fingerprint;
     HDNode hdnode;
+    bool private_key_set;
 } mp_obj_HDNode_t;
 
 STATIC const mp_obj_type_t mod_trezorcrypto_HDNode_type;
@@ -110,8 +111,10 @@ STATIC mp_obj_t mod_trezorcrypto_HDNode_make_new(const mp_obj_type_t *type, size
     }
     if (32 == private_key.len) {
         memcpy(o->hdnode.private_key, private_key.buf, 32);
+        o->private_key_set = true;
     } else {
         memzero(o->hdnode.private_key, 32);
+        o->private_key_set = false;
     }
     if (33 == public_key.len) {
         memcpy(o->hdnode.public_key, public_key.buf, 33);
@@ -123,16 +126,27 @@ STATIC mp_obj_t mod_trezorcrypto_HDNode_make_new(const mp_obj_type_t *type, size
     return MP_OBJ_FROM_PTR(o);
 }
 
-/// def derive(self, index: int) -> None:
+/// def derive(self, index: int, public: bool=False) -> None:
 ///     '''
 ///     Derive a BIP0032 child node in place.
 ///     '''
-STATIC mp_obj_t mod_trezorcrypto_HDNode_derive(mp_obj_t self, mp_obj_t index) {
-    mp_obj_HDNode_t *o = MP_OBJ_TO_PTR(self);
-    uint32_t i = mp_obj_get_int_truncated(index);
+STATIC mp_obj_t mod_trezorcrypto_HDNode_derive(size_t n_args, const mp_obj_t *args) {
+    mp_obj_HDNode_t *o = MP_OBJ_TO_PTR(args[0]);
+    uint32_t i = mp_obj_get_int_truncated(args[1]);
     uint32_t fp = hdnode_fingerprint(&o->hdnode);
+    bool public = n_args > 2 && args[2] == mp_const_true;
 
-    if (!hdnode_private_ckd(&o->hdnode, i)) {
+    int res;
+    if (public) {
+        res = hdnode_public_ckd(&o->hdnode, i);
+    } else {
+        if (!o->private_key_set) {
+            memzero(&o->hdnode, sizeof(o->hdnode));
+            mp_raise_ValueError("Failed to derive, private key not set");
+        }
+        res = hdnode_private_ckd(&o->hdnode, i);
+    }
+    if (!res) {
         memzero(&o->hdnode, sizeof(o->hdnode));
         mp_raise_ValueError("Failed to derive");
     }
@@ -140,7 +154,7 @@ STATIC mp_obj_t mod_trezorcrypto_HDNode_derive(mp_obj_t self, mp_obj_t index) {
 
     return mp_const_none;
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_trezorcrypto_HDNode_derive_obj, mod_trezorcrypto_HDNode_derive);
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorcrypto_HDNode_derive_obj, 2, 3, mod_trezorcrypto_HDNode_derive);
 
 /// def derive_path(self, path: List[int]) -> None:
 ///     '''