diff --git a/src/orbel/orbel.f90 b/src/orbel/orbel.f90
index 9e7a571eb..0a4416160 100644
--- a/src/orbel/orbel.f90
+++ b/src/orbel/orbel.f90
@@ -1037,6 +1037,7 @@ pure module subroutine orbel_xv2el(mu, px, py, pz, vx, vy, vz, a, e, inc, capom,
          rdot = sign(sqrt(v2 - (h / r)**2),rdotv)
          sf = a * (1.0_DP - e**2) / (h * e) * rdot
          f = atan2(sf,cf)
+         if (f < 0.0_DP) f = f + TWOPI
       else
          f = u
       end if