diff --git a/src/Filtering/OnlineFilter.cs b/src/Filtering/OnlineFilter.cs
index 408db4a..e4a02d3 100644
--- a/src/Filtering/OnlineFilter.cs
+++ b/src/Filtering/OnlineFilter.cs
@@ -47,7 +47,7 @@ public static OnlineFilter CreateLowpass(ImpulseResponse mode, double sampleRate
         {
             if (mode == ImpulseResponse.Finite)
             {
-                double[] c = FirCoefficients.LowPass(sampleRate, cutoffRate, order >> 1);
+                double[] c = FirCoefficients.LowPass(sampleRate, cutoffRate, 1, order >> 1);
                 return new OnlineFirFilter(c);
             }