diff --git a/test/rotationtest.cc b/test/rotationtest.cc
index 62ba518d6e819455aa68ff83c51e148d0bedd657..bf349d2f9c21bc4f762d92fc62df652cb28c2493 100644
--- a/test/rotationtest.cc
+++ b/test/rotationtest.cc
@@ -186,8 +186,8 @@ void testDerivativeOfInterpolatedPosition()
                         parDer /= intervalLength;
 
                     // Compute analytical velocity vector gradient
-                    RodLocalStiffness<OneDGrid,double>::interpolationVelocityDerivative(q[i], q[j], s, intervalLength, grad);
-                    
+                    RodLocalStiffness<OneDGrid,double>::interpolationVelocityDerivative(q[i], q[j], s*intervalLength, intervalLength, grad);
+
                     for (int m=0; m<6; m++) {
                         Quaternion<double> diff = fdGrad[m];
                         diff -= grad[m];