diff --git a/src/init.c b/src/init.c
index 55ac059..5514ce3 100644
--- a/src/init.c
+++ b/src/init.c
@@ -28,7 +28,7 @@ static int jac(double phi, const double y[], double *dfdy, double dfdphi[], void
   gsl_matrix *m = &dfdy_mat.matrix;
   gsl_matrix_set(m, 0, 0, 0.0);
   gsl_matrix_set(m, 0, 1, 1.0);
-  gsl_matrix_set(m, 1, 0, 63*M*y[0]-1.0);
+  gsl_matrix_set(m, 1, 0, 6*M*y[0]-1.0);
   gsl_matrix_set(m, 1, 1, 0.0);
 
   dfdphi[0] = 0.0;