diff --git a/tests/orbit_test.cpp b/tests/orbit_test.cpp
index b04355c..ac778d8 100644
--- a/tests/orbit_test.cpp
+++ b/tests/orbit_test.cpp
@@ -24,8 +24,8 @@ TEST_CASE("orbit propagation", "[orbits]")
 	double mu = 398601.68;	// NOTE: gravitational parameter
 	double r = 6378;		// NOTE: body radius in km
 	double initial_anom = 260 * M_PI / 180; // NOTE: radians
+	double time_step = 60 * 50; // NOTE: seconds
 	system_2body sys = systemInit(gravBodyInit(mu, r), orbitInit(a, e));
-	sys.time_step = 60 * 50; // NOTE: seconds
 
 	double E1 = getEccAnomFromTrueAnom(sys.ep.e, initial_anom);
 	REQUIRE_THAT(E1, WithinAbs(-0.8615, 1e-4));
@@ -36,17 +36,17 @@ TEST_CASE("orbit propagation", "[orbits]")
 	double n = getMeanMotion(sys.body.mu, sys.ep.a);
 	REQUIRE_THAT(n, WithinAbs(0.00014582, 1e-8));
 
-	double M2 = getPropagatedMeanAnom(M1, n, sys.time_step);
+	double M2 = getPropagatedMeanAnom(M1, n, time_step);
 	REQUIRE_THAT(M2, WithinAbs(0.1383, 1e-5));
 
 	// TODO: could also test for the other trial values listed in table 4.1
 	double E2_1 = getInitialTrialValue(M2, sys.ep.e);
 	REQUIRE_THAT(E2_1, WithinAbs(0.315452, 1e-5));
 
-	double ecc_anom = getPropagatedEccAnomaly(sys, initial_anom);
+	double ecc_anom = getPropagatedEccAnomaly(sys, initial_anom, time_step);
 	REQUIRE_THAT(ecc_anom, WithinAbs(0.481518, 1e-5));
 
-	double true_anom = getPropagatedTrueAnomaly(sys, initial_anom);
+	double true_anom = getPropagatedTrueAnomaly(sys, initial_anom, time_step);
 	REQUIRE_THAT(true_anom, WithinAbs(1.1339, 1e-4));
 
 	double r2 = orbitGetRadialDistance(sys.ep.e, sys.ep.p, true_anom);