diff --git a/benchmarks/bench_ec_g1.nim b/benchmarks/bench_ec_g1.nim
index 3925474..54b962f 100644
--- a/benchmarks/bench_ec_g1.nim
+++ b/benchmarks/bench_ec_g1.nim
@@ -48,6 +48,7 @@ proc main() =
     addBench(ECP_ShortW_Proj[Fp[curve], NotOnTwist], Iters)
     addBench(ECP_ShortW_Jac[Fp[curve], NotOnTwist], Iters)
     mixedAddBench(ECP_ShortW_Proj[Fp[curve], NotOnTwist], Iters)
+    mixedAddBench(ECP_ShortW_Jac[Fp[curve], NotOnTwist], Iters)
     doublingBench(ECP_ShortW_Proj[Fp[curve], NotOnTwist], Iters)
     doublingBench(ECP_ShortW_Jac[Fp[curve], NotOnTwist], Iters)
     separator()
diff --git a/benchmarks/bench_ec_g2.nim b/benchmarks/bench_ec_g2.nim
index 22a4829..d737db5 100644
--- a/benchmarks/bench_ec_g2.nim
+++ b/benchmarks/bench_ec_g2.nim
@@ -49,6 +49,7 @@ proc main() =
     addBench(ECP_ShortW_Proj[Fp2[curve], OnTwist], Iters)
     addBench(ECP_ShortW_Jac[Fp2[curve], OnTwist], Iters)
     mixedAddBench(ECP_ShortW_Proj[Fp2[curve], OnTwist], Iters)
+    mixedAddBench(ECP_ShortW_Jac[Fp2[curve], OnTwist], Iters)
     doublingBench(ECP_ShortW_Proj[Fp2[curve], OnTwist], Iters)
     doublingBench(ECP_ShortW_Jac[Fp2[curve], OnTwist], Iters)
     separator()
diff --git a/benchmarks/bench_elliptic_template.nim b/benchmarks/bench_elliptic_template.nim
index cd60a7b..6870855 100644
--- a/benchmarks/bench_elliptic_template.nim
+++ b/benchmarks/bench_elliptic_template.nim
@@ -17,7 +17,11 @@ import
   ../constantine/config/[curves, common],
   ../constantine/arithmetic,
   ../constantine/io/io_bigints,
-  ../constantine/elliptic/[ec_shortweierstrass_affine, ec_shortweierstrass_projective, ec_scalar_mul, ec_endomorphism_accel],
+  ../constantine/elliptic/[
+    ec_shortweierstrass_affine,
+    ec_shortweierstrass_projective,
+    ec_shortweierstrass_jacobian,
+    ec_scalar_mul, ec_endomorphism_accel],
   # Helpers
   ../helpers/[prng_unsafe, static_for],
   ./platforms,
@@ -64,7 +68,10 @@ proc mixedAddBench*(T: typedesc, iters: int) =
   let P = rng.random_unsafe(T)
   let Q = rng.random_unsafe(T)
   var Qaff: ECP_ShortW_Aff[T.F, T.Tw]
-  Qaff.affineFromProjective(Q)
+  when Q is ECP_ShortW_Proj:
+    Qaff.affineFromProjective(Q)
+  else:
+    Qaff.affineFromJacobian(Q)
   bench("EC Mixed Addition " & G1_or_G2, T, iters):
     r.madd(P, Qaff)
 
diff --git a/constantine.nimble b/constantine.nimble
index 7a257a8..9a7236d 100644
--- a/constantine.nimble
+++ b/constantine.nimble
@@ -75,7 +75,7 @@ const testDesc: seq[tuple[path: string, useGMP: bool]] = @[
   # ("tests/t_ec_shortw_jac_g1_mul_sanity.nim", false),
   # ("tests/t_ec_shortw_jac_g1_mul_distri.nim", false),
   ("tests/t_ec_shortw_jac_g1_mul_vs_ref.nim", false),
-  # mixed_add
+  ("tests/t_ec_shortw_jac_g1_mixed_add.nim", false),
 
   # Elliptic curve arithmetic G2
   # ----------------------------------------------------------
@@ -107,25 +107,25 @@ const testDesc: seq[tuple[path: string, useGMP: bool]] = @[
   # ("tests/t_ec_shortw_jac_g2_mul_sanity_bn254_snarks.nim", false),
   # ("tests/t_ec_shortw_jac_g2_mul_distri_bn254_snarks.nim", false),
   ("tests/t_ec_shortw_jac_g2_mul_vs_ref_bn254_snarks.nim", false),
-  # mixed_add
+  ("tests/t_ec_shortw_jac_g2_mixed_add_bn254_snarks.nim", false),
 
   # ("tests/t_ec_shortw_jac_g2_add_double_bls12_381.nim", false),
   # ("tests/t_ec_shortw_jac_g2_mul_sanity_bls12_381.nim", false),
   # ("tests/t_ec_shortw_jac_g2_mul_distri_bls12_381.nim", false),
   ("tests/t_ec_shortw_jac_g2_mul_vs_ref_bls12_381.nim", false),
-  # mixed_add
+  ("tests/t_ec_shortw_jac_g2_mixed_add_bls12_381.nim", false),
 
   # ("tests/t_ec_shortw_jac_g2_add_double_bls12_377.nim", false),
   # ("tests/t_ec_shortw_jac_g2_mul_sanity_bls12_377.nim", false),
   # ("tests/t_ec_shortw_jac_g2_mul_distri_bls12_377.nim", false),
   ("tests/t_ec_shortw_jac_g2_mul_vs_ref_bls12_377.nim", false),
-  # mixed_add
+  ("tests/t_ec_shortw_jac_g2_mixed_add_bls12_377.nim", false),
 
   # ("tests/t_ec_shortw_jac_g2_add_double_bw6_761.nim", false),
   # ("tests/t_ec_shortw_jac_g2_mul_sanity_bw6_761.nim", false),
   # ("tests/t_ec_shortw_jac_g2_mul_distri_bw6_761.nim", false),
   ("tests/t_ec_shortw_jac_g2_mul_vs_ref_bw6_761.nim", false),
-  # mixed_add
+  ("tests/t_ec_shortw_jac_g2_mixed_add_bw6_761.nim", false),
 
   # Elliptic curve arithmetic vs Sagemath
   # ----------------------------------------------------------
diff --git a/constantine/arithmetic/limbs.nim b/constantine/arithmetic/limbs.nim
index cb46557..01d3342 100644
--- a/constantine/arithmetic/limbs.nim
+++ b/constantine/arithmetic/limbs.nim
@@ -63,13 +63,14 @@ when UseASM_X86_64:
 
 func setZero*(a: var Limbs) =
   ## Set ``a`` to 0
-  zeroMem(a[0].addr, sizeof(a))
+  for i in 0 ..< a.len:
+    a[i] = Zero
 
 func setOne*(a: var Limbs) =
   ## Set ``a`` to 1
   a[0] = One
-  when a.len > 1:
-    zeroMem(a[1].addr, (a.len - 1) * sizeof(SecretWord))
+  for i in 1 ..< a.len:
+    a[i] = Zero
 
 func setUint*(a: var Limbs, n: SomeUnsignedInt) =
   ## set ``a`` to an unsigned integer ``n``
diff --git a/constantine/elliptic/ec_shortweierstrass_affine.nim b/constantine/elliptic/ec_shortweierstrass_affine.nim
index 6d4aa29..71f7fc4 100644
--- a/constantine/elliptic/ec_shortweierstrass_affine.nim
+++ b/constantine/elliptic/ec_shortweierstrass_affine.nim
@@ -32,6 +32,16 @@ type
     ## over a field F
     x*, y*: F
 
+func isInf*(P: ECP_ShortW_Aff): SecretBool =
+  ## Returns true if P is an infinity point
+  ## and false otherwise
+  ##
+  ## Note: the jacobian coordinates equation is
+  ##       Y² = X³ + aXZ⁴ + bZ⁶
+  ## A "zero" point is any point with coordinates X and Z = 0
+  ## Y can be anything
+  result = P.x.isZero() and P.y.isZero()
+
 func curve_eq_rhs*[F](y2: var F, x: F, Tw: static Twisted) =
   ## Compute the curve equation right-hand-side from field element `x`
   ## i.e.  `y²` in `y² = x³ + a x + b`
diff --git a/constantine/elliptic/ec_shortweierstrass_jacobian.nim b/constantine/elliptic/ec_shortweierstrass_jacobian.nim
index ffc81ee..5883cc6 100644
--- a/constantine/elliptic/ec_shortweierstrass_jacobian.nim
+++ b/constantine/elliptic/ec_shortweierstrass_jacobian.nim
@@ -291,6 +291,85 @@ func sum*[F; Tw: static Twisted](
     r.ccopy(Q, P.isInf())
     r.ccopy(P, Q.isInf())
 
+func madd*[F; Tw: static Twisted](
+       r: var ECP_ShortW_Jac[F, Tw],
+       P: ECP_ShortW_Jac[F, Tw],
+       Q: ECP_ShortW_Aff[F, Tw]
+     ) =
+  ## Elliptic curve mixed addition for Short Weierstrass curves
+  ## with p in Jacobian coordinates and Q in affine coordinates
+  ##
+  ##   R = P + Q
+  # "madd-2007-bl" mixed addition formula - https://hyperelliptic.org/EFD/g1p/auto-shortw-jacobian-0.html#addition-madd-2007-bl
+  # with conditional copies to handle infinity points
+  #  Assumptions: Z2=1.
+  #  Cost: 7M + 4S + 9add + 3*2 + 1*4.
+  #  Source: 2007 Bernstein–Lange.
+  #  Explicit formulas:
+  #
+  #        Z1Z1 = Z1²
+  #        U2 = X2*Z1Z1
+  #        S2 = Y2*Z1*Z1Z1
+  #        H = U2-X1
+  #        HH = H2
+  #        I = 4*HH
+  #        J = H*I
+  #        r = 2*(S2-Y1)
+  #        V = X1*I
+  #        X3 = r²-J-2*V
+  #        Y3 = r*(V-X3)-2*Y1*J
+  #        Z3 = (Z1+H)²-Z1Z1-HH
+  var Z1Z1 {.noInit.}, H {.noInit.}, HH {.noInit.}, I{.noInit.}, J {.noInit.}: F
+
+  # Preload P and Q in cache
+  let pIsInf = P.isInf()
+  let qIsInf = Q.isInf()
+
+  Z1Z1.square(P.z)    # Z₁Z₁ = Z₁²
+  r.z.prod(P.z, Z1Z1) #               P.Z is hot in cache, keep it in same register.
+  r.z *= Q.y          # S₂ = Y₂Z₁Z₁Z₁         -- r.z used as S₂
+
+  H.prod(Q.x, Z1Z1)   # U₂ = X₂Z₁Z₁
+  H -= P.x            # H = U₂ - X₁
+
+  HH.square(H)        # HH = H²
+
+  I.double(HH)
+  I.double()          # I = 4HH
+
+  J.prod(H, I)        # J = H*I
+  r.y.prod(P.x, I)    # V = X₁*I              -- r.y used as V
+
+  r.z -= P.y          #
+  r.z.double()        # r = 2*(S₂-Y₁)         -- r.z used as r
+
+  r.x.square(r.z)     # r²
+  r.x -= J
+  r.x -= r.y
+  r.x -= r.y          # X₃ = r²-J-2*V         -- r.x computed
+
+  r.y -= r.x          # V-X₃
+  r.y *= r.z          # r*(V-X₃)
+
+  J *= P.y            # Y₁J                   -- J reused as Y₁J
+  r.y -= J
+  r.y -= J            # Y₃ = r*(V-X₃) - 2*Y₁J -- r.y computed
+
+  r.z.sum(P.z, H)     # Z₁ + H
+  r.z.square()
+  r.z -= Z1Z1
+  r.z -= HH           # Z₃ = (Z1+H)²-Z1Z1-HH
+
+  # Now handle points at infinity
+  proc one(): F =
+    result.setOne()
+
+  r.x.ccopy(Q.x, pIsInf)
+  r.y.ccopy(Q.y, pIsInf)
+  r.z.ccopy(static(one()), pIsInf)
+
+  r.ccopy(P, qIsInf)
+
 func double*[F; Tw: static Twisted](
        r: var ECP_ShortW_Jac[F, Tw],
        P: ECP_ShortW_Jac[F, Tw]
@@ -373,13 +452,13 @@ func diff*(r: var ECP_ShortW_Jac,
 func affineFromJacobian*[F; Tw](
        aff: var ECP_ShortW_Aff[F, Tw],
        jac: ECP_ShortW_Jac[F, Tw]) =
-  var invZ {.noInit.}, invZ2: F
+  var invZ {.noInit.}, invZ2{.noInit.}: F
   invZ.inv(jac.z)
   invZ2.square(invZ)
 
   aff.x.prod(jac.x, invZ2)
   aff.y.prod(jac.y, invZ)
-  aff.y.prod(jac.y, invZ2)
+  aff.y *= invZ2
 
 func jacobianFromAffine*[F; Tw](
        jac: var ECP_ShortW_Jac[F, Tw],
diff --git a/tests/t_ec_shortw_jac_g1_mixed_add.nim b/tests/t_ec_shortw_jac_g1_mixed_add.nim
new file mode 100644
index 0000000..e90356b
--- /dev/null
+++ b/tests/t_ec_shortw_jac_g1_mixed_add.nim
@@ -0,0 +1,42 @@
+# Constantine
+# Copyright (c) 2018-2019    Status Research & Development GmbH
+# Copyright (c) 2020-Present Mamy André-Ratsimbazafy
+# Licensed and distributed under either of
+#   * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
+#   * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
+# at your option. This file may not be copied, modified, or distributed except according to those terms.
+
+import
+  # Internals
+  ../constantine/config/curves,
+  ../constantine/elliptic/ec_shortweierstrass_jacobian,
+  ../constantine/arithmetic,
+  # Test utilities
+  ./t_ec_template
+
+const
+  Iters = 12
+
+run_EC_mixed_add_impl(
+    ec = ECP_ShortW_Jac[Fp[BN254_Snarks], NotOnTwist],
+    Iters = Iters,
+    moduleName = "test_ec_shortweierstrass_jacobian_mixed_add_" & $BN254_Snarks
+  )
+
+run_EC_mixed_add_impl(
+    ec = ECP_ShortW_Jac[Fp[BLS12_381], NotOnTwist],
+    Iters = Iters,
+    moduleName = "test_ec_shortweierstrass_jacobian_mixed_add_" & $BLS12_381
+  )
+
+run_EC_mixed_add_impl(
+    ec = ECP_ShortW_Jac[Fp[BLS12_377], NotOnTwist],
+    Iters = Iters,
+    moduleName = "test_ec_shortweierstrass_jacobian_mixed_add_" & $BLS12_377
+  )
+
+run_EC_mixed_add_impl(
+    ec = ECP_ShortW_Jac[Fp[BW6_761], NotOnTwist],
+    Iters = Iters,
+    moduleName = "test_ec_shortweierstrass_jacobian_mixed_add_" & $BW6_761
+  )
diff --git a/tests/t_ec_template.nim b/tests/t_ec_template.nim
index 6df17d0..aa128df 100644
--- a/tests/t_ec_template.nim
+++ b/tests/t_ec_template.nim
@@ -441,7 +441,10 @@ proc run_EC_mixed_add_impl*(
           let a = rng.random_point(EC, randZ, gen)
           let b = rng.random_point(EC, randZ, gen)
           var bAff: ECP_ShortW_Aff[EC.F, EC.Tw]
-          bAff.affineFromProjective(b)
+          when b is ECP_ShortW_Proj:
+            bAff.affineFromProjective(b)
+          else:
+            bAff.affineFromJacobian(b)
 
           var r_generic, r_mixed: EC