diff --git a/crypto/ec/ecp_smpl.c b/crypto/ec/ecp_smpl.c
index 7ac519ca03..d0c5557ff4 100644
--- a/crypto/ec/ecp_smpl.c
+++ b/crypto/ec/ecp_smpl.c
@@ -1483,10 +1483,10 @@ int ec_GFp_simple_ladder_pre(const EC_GROUP *group,
 }
 
 /*-
- * Differential addition-and-doubling using  Eq. (8) and (10) from Izu-Takagi
+ * Differential addition-and-doubling using  Eq. (9) and (10) from Izu-Takagi
  * "A fast parallel elliptic curve multiplication resistant against side channel
  * attacks", as described at
- * https://hyperelliptic.org/EFD/g1p/auto-shortw-xz.html#ladder-ladd-2002-it-3
+ * https://hyperelliptic.org/EFD/g1p/auto-shortw-xz.html#ladder-ladd-2002-it-4
  */
 int ec_GFp_simple_ladder_step(const EC_GROUP *group,
                               EC_POINT *r, EC_POINT *s,
@@ -1511,39 +1511,42 @@ int ec_GFp_simple_ladder_step(const EC_GROUP *group,
         || !group->meth->field_mul(group, t2, r->X, s->Z, ctx)
         || !group->meth->field_mul(group, t3, r->Z, s->X, ctx)
         || !group->meth->field_mul(group, t4, group->a, t1, ctx)
-        || !BN_mod_sub_quick(t4, t0, t4, group->field)
-        || !BN_mod_add_quick(t5, t3, t2, group->field)
-        || !group->meth->field_sqr(group, t4, t4, ctx)
-        || !group->meth->field_mul(group, t5, t1, t5, ctx)
-        || !BN_mod_lshift_quick(t0, group->b, 2, group->field)
-        || !group->meth->field_mul(group, t5, t0, t5, ctx)
-        || !BN_mod_sub_quick(t5, t4, t5, group->field)
+        || !BN_mod_add_quick(t0, t0, t4, group->field)
+        || !BN_mod_add_quick(t4, t3, t2, group->field)
+        || !group->meth->field_mul(group, t0, t4, t0, ctx)
+        || !group->meth->field_sqr(group, t1, t1, ctx)
+        || !BN_mod_lshift_quick(t7, group->b, 2, group->field)
+        || !group->meth->field_mul(group, t1, t7, t1, ctx)
+        || !BN_mod_lshift1_quick(t0, t0, group->field)
+        || !BN_mod_add_quick(t0, t1, t0, group->field)
+        || !BN_mod_sub_quick(t1, t2, t3, group->field)
+        || !group->meth->field_sqr(group, t1, t1, ctx)
+        || !group->meth->field_mul(group, t3, t1, p->X, ctx)
+        || !group->meth->field_mul(group, t0, p->Z, t0, ctx)
         /* s->X coord output */
-        || !group->meth->field_mul(group, s->X, t5, p->Z, ctx)
-        || !BN_mod_sub_quick(t3, t2, t3, group->field)
-        || !group->meth->field_sqr(group, t3, t3, ctx)
+        || !BN_mod_sub_quick(s->X, t0, t3, group->field)
         /* s->Z coord output */
-        || !group->meth->field_mul(group, s->Z, t3, p->X, ctx)
-        || !group->meth->field_sqr(group, t2, r->X, ctx)
-        || !group->meth->field_sqr(group, t4, r->Z, ctx)
-        || !group->meth->field_mul(group, t1, t4, group->a, ctx)
-        || !BN_mod_add_quick(t6, r->X, r->Z, group->field)
+        || !group->meth->field_mul(group, s->Z, p->Z, t1, ctx)
+        || !group->meth->field_sqr(group, t3, r->X, ctx)
+        || !group->meth->field_sqr(group, t2, r->Z, ctx)
+        || !group->meth->field_mul(group, t4, t2, group->a, ctx)
+        || !BN_mod_add_quick(t5, r->X, r->Z, group->field)
+        || !group->meth->field_sqr(group, t5, t5, ctx)
+        || !BN_mod_sub_quick(t5, t5, t3, group->field)
+        || !BN_mod_sub_quick(t5, t5, t2, group->field)
+        || !BN_mod_sub_quick(t6, t3, t4, group->field)
         || !group->meth->field_sqr(group, t6, t6, ctx)
-        || !BN_mod_sub_quick(t6, t6, t2, group->field)
-        || !BN_mod_sub_quick(t6, t6, t4, group->field)
-        || !BN_mod_sub_quick(t7, t2, t1, group->field)
-        || !group->meth->field_sqr(group, t7, t7, ctx)
-        || !group->meth->field_mul(group, t5, t4, t6, ctx)
-        || !group->meth->field_mul(group, t5, t0, t5, ctx)
+        || !group->meth->field_mul(group, t0, t2, t5, ctx)
+        || !group->meth->field_mul(group, t0, t7, t0, ctx)
         /* r->X coord output */
-        || !BN_mod_sub_quick(r->X, t7, t5, group->field)
-        || !BN_mod_add_quick(t2, t2, t1, group->field)
-        || !group->meth->field_sqr(group, t5, t4, ctx)
-        || !group->meth->field_mul(group, t5, t5, t0, ctx)
-        || !group->meth->field_mul(group, t6, t6, t2, ctx)
-        || !BN_mod_lshift1_quick(t6, t6, group->field)
+        || !BN_mod_sub_quick(r->X, t6, t0, group->field)
+        || !BN_mod_add_quick(t6, t3, t4, group->field)
+        || !group->meth->field_sqr(group, t3, t2, ctx)
+        || !group->meth->field_mul(group, t7, t3, t7, ctx)
+        || !group->meth->field_mul(group, t5, t5, t6, ctx)
+        || !BN_mod_lshift1_quick(t5, t5, group->field)
         /* r->Z coord output */
-        || !BN_mod_add_quick(r->Z, t5, t6, group->field))
+        || !BN_mod_add_quick(r->Z, t7, t5, group->field))
         goto err;
 
     ret = 1;
diff --git a/test/recipes/30-test_evp_data/evppkey_ecc.txt b/test/recipes/30-test_evp_data/evppkey_ecc.txt
index 685af17994..8e95c02349 100644
--- a/test/recipes/30-test_evp_data/evppkey_ecc.txt
+++ b/test/recipes/30-test_evp_data/evppkey_ecc.txt
@@ -4364,3 +4364,240 @@ PeerKey=ALICE_cf_wap-wsg-idm-ecid-wtls9_PUB
 SharedSecret=948d3030e95cead39a1bb3d8a01c2be178517ba7
 
 # tests: 484
+
+Title=zero x-coord regression tests
+
+PrivateKey=ALICE_zero_prime192v1
+-----BEGIN PRIVATE KEY-----
+MDkCAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQEEHzAdAgEBBBhaPNk8jG5hSG6y8tUqUoOaNNsZ3APU
+pps=
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_prime192v1_PUB
+-----BEGIN PUBLIC KEY-----
+MEkwEwYHKoZIzj0CAQYIKoZIzj0DAQEDMgAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAe2hWBe5g
+DLNj216pEvK7XjoKLg5gNg8S
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_prime192v1
+PeerKey=BOB_zero_prime192v1_PUB
+SharedSecret=baaffd49a8399d2ad52cbbe24d47b67afb4b3cf436f1cd65
+
+PrivateKey=ALICE_zero_prime192v2
+-----BEGIN PRIVATE KEY-----
+MDkCAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQIEHzAdAgEBBBj1AIQMJ7jqYIKCvxYAS+qKMmKmH0to
+41k=
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_prime192v2_PUB
+-----BEGIN PUBLIC KEY-----
+MEkwEwYHKoZIzj0CAQYIKoZIzj0DAQIDMgAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAB4Gj7Qqt
+2wx/jwFlKgvE4rnd50LspdMk
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_prime192v2
+PeerKey=BOB_zero_prime192v2_PUB
+SharedSecret=b8f200a4b87064f2e8600685ca3e69b8e661a117aabc770b
+
+PrivateKey=ALICE_zero_prime192v3
+-----BEGIN PRIVATE KEY-----
+MDkCAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQMEHzAdAgEBBBh/maLQMSlea9BfLqGy5NPuK0YAH/cz
+GqI=
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_prime192v3_PUB
+-----BEGIN PUBLIC KEY-----
+MEkwEwYHKoZIzj0CAQYIKoZIzj0DAQMDMgAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAZEzb63e2
+3MKatRLR9Y1M5JEdI9jwMocI
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_prime192v3
+PeerKey=BOB_zero_prime192v3_PUB
+SharedSecret=b5de857d355bc5b9e270a4c290ea9728d764d8b243ff5d8d
+
+PrivateKey=ALICE_zero_prime239v1
+-----BEGIN PRIVATE KEY-----
+MD8CAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQQEJTAjAgEBBB5pYWzRYI+c6O7NXCt0H2kw8XRL3rhe
+4MrJT8j++CI=
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_prime239v1_PUB
+-----BEGIN PUBLIC KEY-----
+MFUwEwYHKoZIzj0CAQYIKoZIzj0DAQQDPgAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+Ox02uwNNLFuvDRn5ip8TxvW0W22R7UzJa9Av6/nh
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_prime239v1
+PeerKey=BOB_zero_prime239v1_PUB
+SharedSecret=6b6206408bd05d42daa2cd224c401a1230b44e184f17b82f385f22dac215
+
+PrivateKey=ALICE_zero_prime239v2
+-----BEGIN PRIVATE KEY-----
+MD8CAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQUEJTAjAgEBBB5l8bB7Cpmr7vyx9FiOT2wEF3YOFbDG
+bmRr3Vi/xr4=
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_prime239v2_PUB
+-----BEGIN PUBLIC KEY-----
+MFUwEwYHKoZIzj0CAQYIKoZIzj0DAQUDPgAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+IOg3VJGQ89d1GWg4Igxcj5xpDmJiP8tv+e4mxt5U
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_prime239v2
+PeerKey=BOB_zero_prime239v2_PUB
+SharedSecret=772c2819c960c78f28f21f6542b7409294fad1f84567c44c4b7678dc0e42
+
+PrivateKey=ALICE_zero_prime239v3
+-----BEGIN PRIVATE KEY-----
+MD8CAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQYEJTAjAgEBBB5HF5FABzUOTYMZg9UdZTx/oRERm/fU
+M/+otKzpLjA=
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_prime239v3_PUB
+-----BEGIN PUBLIC KEY-----
+MFUwEwYHKoZIzj0CAQYIKoZIzj0DAQYDPgAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+AsZ4u6r3qQI78EYBpiSgWjqNpoeShjr5piecMBWj
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_prime239v3
+PeerKey=BOB_zero_prime239v3_PUB
+SharedSecret=56a71f5dd1611e8032c3e2d8224d86e5e8c2fc6480d74c0e282282decd43
+
+PrivateKey=ALICE_zero_prime256v1
+-----BEGIN PRIVATE KEY-----
+MEECAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQcEJzAlAgEBBCDXhMb6aR4JR2+l2tmgYqP0r8S4jtym
+yH++awvF2nGhhg==
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_prime256v1_PUB
+-----BEGIN PUBLIC KEY-----
+MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+AABmSFx4Di+D1yQzvV2EoGu2VBwq8x2uhxcov4VqF0+T9A==
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_prime256v1
+PeerKey=BOB_zero_prime256v1_PUB
+SharedSecret=c4f5607deb8501f1a4ba23fce4122a4343a17ada2c86a9c8e0d03d92d4a4c84c
+
+PrivateKey=ALICE_zero_secp112r2
+-----BEGIN PRIVATE KEY-----
+MCwCAQAwEAYHKoZIzj0CAQYFK4EEAAcEFTATAgEBBA4hh3tRkG3tnA0496ffMw==
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_secp112r2_PUB
+-----BEGIN PUBLIC KEY-----
+MDIwEAYHKoZIzj0CAQYFK4EEAAcDHgAEAAAAAAAAAAAAAAAAAAAS5eEOWDV/Wk7w4djyDQ==
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_secp112r2
+PeerKey=BOB_zero_secp112r2_PUB
+SharedSecret=958cc1cb425713678830a4d7d95e
+
+PrivateKey=ALICE_zero_secp128r1
+-----BEGIN PRIVATE KEY-----
+MC4CAQAwEAYHKoZIzj0CAQYFK4EEABwEFzAVAgEBBBCykSzic/h3T2K6SkSP1SGt
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_secp128r1_PUB
+-----BEGIN PUBLIC KEY-----
+MDYwEAYHKoZIzj0CAQYFK4EEABwDIgAEAAAAAAAAAAAAAAAAAAAAAABya8M5aeOpNG3z799IdHc=
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_secp128r1
+PeerKey=BOB_zero_secp128r1_PUB
+SharedSecret=5235d452066f126cd7e99eea00fd3068
+
+PrivateKey=ALICE_zero_secp160r1
+-----BEGIN PRIVATE KEY-----
+MDMCAQAwEAYHKoZIzj0CAQYFK4EEAAgEHDAaAgEBBBUACoRnbig69XLlh5VcRexpbbn5zwA=
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_secp160r1_PUB
+-----BEGIN PUBLIC KEY-----
+MD4wEAYHKoZIzj0CAQYFK4EEAAgDKgAEAAAAAAAAAAAAAAAAAAAAAAAAAAAG/w1po29wYlxlygXs
+MGfbiGg5ng==
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_secp160r1
+PeerKey=BOB_zero_secp160r1_PUB
+SharedSecret=9ccd0ab8d093b6acdb3fe14c3736a0dfe61a4666
+
+PrivateKey=ALICE_zero_secp160r2
+-----BEGIN PRIVATE KEY-----
+MDMCAQAwEAYHKoZIzj0CAQYFK4EEAB4EHDAaAgEBBBUAQFGxInSw1eAvd45E9TUdbXtJGnA=
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_secp160r2_PUB
+-----BEGIN PUBLIC KEY-----
+MD4wEAYHKoZIzj0CAQYFK4EEAB4DKgAEAAAAAAAAAAAAAAAAAAAAAAAAAAAZtSBSZqfmXp47v5z2
+ZZZl2JFxDg==
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_secp160r2
+PeerKey=BOB_zero_secp160r2_PUB
+SharedSecret=303e0a282ac86f463fe834cb51b0057be42ed5ab
+
+PrivateKey=ALICE_zero_secp384r1
+-----BEGIN PRIVATE KEY-----
+ME4CAQAwEAYHKoZIzj0CAQYFK4EEACIENzA1AgEBBDD6kgzKbg28zbQyVTdC0IdHbm0UCQt2Rdbi
+VVHJeYRSnNpFOiFLaOsGOmwoeZzj6jc=
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_secp384r1_PUB
+-----BEGIN PUBLIC KEY-----
+MHYwEAYHKoZIzj0CAQYFK4EEACIDYgAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+AAAAAAAAAAAAAAAAAAAAPPme8E9RpepjC6P5+WDdWToUyb45/SvSFdO0sIqq+Gu/kn8sRuUqsG+3
+QriFDlIe
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_secp384r1
+PeerKey=BOB_zero_secp384r1_PUB
+SharedSecret=b1cfeaeef51dfd487d3a8b2849f1592e04d63f2d2c88b310a6290ebfe5399f5ffe954eabd0619231393e56c35b242986
+
+PrivateKey=ALICE_zero_secp521r1
+-----BEGIN PRIVATE KEY-----
+MGACAQAwEAYHKoZIzj0CAQYFK4EEACMESTBHAgEBBEIAbddDLMUWbAsY7l3vbNDmntXuAUcDYPg5
+w/cgUwSCIvrV9MBeSG8AWqT16riHmHlsn+XI5PAJM6eij3JDahnu9Mo=
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_secp521r1_PUB
+-----BEGIN PUBLIC KEY-----
+MIGbMBAGByqGSM49AgEGBSuBBAAjA4GGAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA0g7J/qa1d8ENJsobtEb0CymeZIsa
+1Qiq0GiJb+4/jmFLxjBU1Xcr8Bpl1BLgvKqOll0vXTMtfzn4RtRArgAfT4c=
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_secp521r1
+PeerKey=BOB_zero_secp521r1_PUB
+SharedSecret=003fc3028f61db94b20c7cd177923b6e73f12f0ab067c9ce8866755e3c82abb39c9863cde74fa80b32520bd7dd0eb156c30c08911503b67b2661f1264d09bb231423
+
+PrivateKey=ALICE_zero_wap-wsg-idm-ecid-wtls7
+-----BEGIN PRIVATE KEY-----
+MDMCAQAwEAYHKoZIzj0CAQYFZysBBAcEHDAaAgEBBBUAoGng7WzYr4P9vtdc3BS/UiNWmc0=
+-----END PRIVATE KEY-----
+
+PublicKey=BOB_zero_wap-wsg-idm-ecid-wtls7_PUB
+-----BEGIN PUBLIC KEY-----
+MD4wEAYHKoZIzj0CAQYFZysBBAcDKgAEAAAAAAAAAAAAAAAAAAAAAAAAAAAZtSBSZqfmXp47v5z2
+ZZZl2JFxDg==
+-----END PUBLIC KEY-----
+
+# ECDH Alice with Bob peer
+Derive=ALICE_zero_wap-wsg-idm-ecid-wtls7
+PeerKey=BOB_zero_wap-wsg-idm-ecid-wtls7_PUB
+SharedSecret=6582fc03bbb340fcf24a5fe8fcdf722655efa8b9
+
+# tests: 14