diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 0.1.2.0 - 2023-03-02
+
+Some values of the Jacobi theta functions were wrong.
+
+
 ## 0.1.1.1 - 2023-03-01
 
 Removed a useless type alias.
diff --git a/jacobi-theta.cabal b/jacobi-theta.cabal
--- a/jacobi-theta.cabal
+++ b/jacobi-theta.cabal
@@ -1,5 +1,5 @@
 name:                jacobi-theta
-version:             0.1.1.1
+version:             0.1.2.0
 synopsis:            Jacobi Theta Functions
 description:         Evaluation of the Jacobi theta functions.
 homepage:            https://github.com/stla/jacobi-theta#readme
diff --git a/src/Math/JacobiTheta.hs b/src/Math/JacobiTheta.hs
--- a/src/Math/JacobiTheta.hs
+++ b/src/Math/JacobiTheta.hs
@@ -64,18 +64,21 @@
           termp = altp * exp (- square (nplus' - 0.5 + z') / t')
           newseries = series + termm + termp
 
-falpha :: Cplx -> Cplx -> Cplx
-falpha z tau = 
-  sqrt (-i_ * tau) * exp (i_ / tau * z * z / pi)
+--falpha :: Cplx -> Cplx -> Cplx
+--falpha z tau = 
+--  sqrt (-i_ * tau) * exp (i_ / tau * z * z / pi)
 
 jtheta1Alt :: Cplx -> Cplx -> Cplx
 jtheta1Alt z tau = 
   if imagPart tau > 1.3 
     then
-      let w = pi * tau in 
-      i_ * jtheta1Alt2 (z / w) (i_ / w) / falpha z tau
+      jtheta1Alt1 z (exp (i_ * pi * tau))
+--      let w = pi * tau in 
+--      i_ * jtheta1Alt2 (z / w) (i_ / w) / falpha z tau
     else
-      i_ * jtheta1Alt1 (z / tau) (exp (-i_ * pi / tau)) / falpha z tau
+      let t = - i_ * tau / pi in
+      jtheta1Alt2 (z / pi) t
+--      i_ * jtheta1Alt1 (z / tau) (exp (-i_ * pi / tau)) / falpha z tau
 
 tauFromQ :: Cplx -> Cplx
 tauFromQ q = -i_ * log q / pi