diff --git a/engine/rk23.go b/engine/rk23.go
index 7bac044aa..a207a743a 100644
--- a/engine/rk23.go
+++ b/engine/rk23.go
@@ -104,7 +104,7 @@ func (rk *RK23) Step() {
 			rlerr = float64(cuda.MaxAbs(errnorm))
 			fail = 1
 		}
-		if fail == 0 || RelErr < 0.0 || rlerr < RelErr || Dt_si <= MinDt || FixDt != 0 { // mindt check to avoid infinite loop
+		if fail == 0 || RelErr <= 0.0 || rlerr < RelErr || Dt_si <= MinDt || FixDt != 0 { // mindt check to avoid infinite loop
 			// step OK
 			setLastErr(err)
 			setMaxTorque(k4)
diff --git a/engine/rk45dp.go b/engine/rk45dp.go
index 4579b5e73..ac453cd4a 100644
--- a/engine/rk45dp.go
+++ b/engine/rk45dp.go
@@ -118,7 +118,7 @@ func (rk *RK45DP) Step() {
 			rlerr = float64(cuda.MaxAbs(errnorm))
 			fail = 1
 		}
-		if fail == 0 || RelErr < 0.0 || rlerr < RelErr || Dt_si <= MinDt || FixDt != 0 { // mindt check to avoid infinite loop
+		if fail == 0 || RelErr <= 0.0 || rlerr < RelErr || Dt_si <= MinDt || FixDt != 0 { // mindt check to avoid infinite loop
 			// step OK
 			setLastErr(err)
 			setMaxTorque(k7)
diff --git a/engine/rk56.go b/engine/rk56.go
index 4cbb91abf..18009b1fb 100644
--- a/engine/rk56.go
+++ b/engine/rk56.go
@@ -128,7 +128,7 @@ func (rk *RK56) Step() {
 			rlerr = float64(cuda.MaxAbs(errnorm))
 			fail = 1
 		}
-		if fail == 0 || RelErr < 0.0 || rlerr < RelErr || Dt_si <= MinDt || FixDt != 0 { // mindt check to avoid infinite loop
+		if fail == 0 || RelErr <= 0.0 || rlerr < RelErr || Dt_si <= MinDt || FixDt != 0 { // mindt check to avoid infinite loop
 			// step OK
 			setLastErr(err)
 			setMaxTorque(k2)