diff --git a/src/orbital_mechanics.cpp b/src/orbital_mechanics.cpp
index a0c01d6..712dcd7 100644
--- a/src/orbital_mechanics.cpp
+++ b/src/orbital_mechanics.cpp
@@ -44,8 +44,8 @@ void orbital_elements_to_cartesian(OrbitalElements elements, double parent_mass,
         double p = a * (1.0 - e * e);
         vx_orbital = -sqrt(mu / p) * sin_nu;
         vy_orbital = sqrt(mu / p) * (e + cos_nu);
-    } else if (fabs(e - 1.0) < 1e-10) {
-        double p = 2.0 * a;
+    } else if (fabs(e - 1.0) < 0.005) {
+        double p = elements.semi_latus_rectum;
         vx_orbital = -sqrt(mu / p) * sin_nu;
         vy_orbital = sqrt(mu / p) * (1.0 + cos_nu);
     } else {
diff --git a/tests/configs/parabolic_comet.toml b/tests/configs/parabolic_comet.toml
index fb8881e..ef0e4f0 100644
--- a/tests/configs/parabolic_comet.toml
+++ b/tests/configs/parabolic_comet.toml
@@ -21,7 +21,7 @@ radius = 5.0e3
 parent_index = 0
 color = {r = 0.7,g = 0.8,b = 0.9 }
 orbit = {
-    semi_latus_rectum = 1.496e11,
+    semi_latus_rectum = 2.992e11,
     eccentricity = 1.0,
     true_anomaly = 0.0
 }