diff --git a/Sources/EcgSynKit/EcgSynKit.swift b/Sources/EcgSynKit/EcgSynKit.swift
index c1834f4..b7a40ac 100644
--- a/Sources/EcgSynKit/EcgSynKit.swift
+++ b/Sources/EcgSynKit/EcgSynKit.swift
@@ -207,7 +207,7 @@ public struct Generator: ~Copyable {
             mt2 = max(t, mt2)
             //print("ip: \(ip) mip: \(mip) mt2: \(mt2)")
 
-            let w0 = 2 * .pi / rrpc[ip]
+            let w0 = 2 * .pi / rrpc[min(ip, rrpc.count - 1)]
 
             let zbase = 0.005 * sin(2 * .pi * fhi * t)