diff --git a/src/utils.jl b/src/utils.jl
index f08823b..93137f7 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -52,7 +52,7 @@ function AllenBerkley_highpass100(x, fs)
     B2 = -R1 * R1   
     A1 = -(1+R1)
 
-    for i = 1:length(x)
+    for i = 1:eachindex(x)
         Y[3] = Y[2]
         Y[2] = Y[1]
         Y[1] = B2*Y[3] + B1*Y[2] + x[i]