diff --git a/Sources/ECGSynKit/ECGSyn.swift b/Sources/ECGSynKit/ECGSyn.swift
index e5926a5..c7506b8 100644
--- a/Sources/ECGSynKit/ECGSyn.swift
+++ b/Sources/ECGSynKit/ECGSyn.swift
@@ -47,7 +47,6 @@ public struct ECGSyn {
     }
 
     public static func generate(params: Parameters, rrSeries: ECGSynRRSeries<Double>) -> [Double] {
-        var rng = rrSeries.rng
         let srInternal = rrSeries.timeParameters.srInternal
 
         let hrSec = rrSeries.timeParameters.hrMean / 60.0
@@ -98,7 +97,7 @@ public struct ECGSyn {
         // add uniformly distributed measurement noise
         for i in 0 ..< zresult.count {
             zresult[i] = (params.range.1 - params.range.0) * (zresult[i] - zmin) / zrange + params.range.0
-            zresult[i] += params.noiseAmplitude * (2.0 * rng.nextDouble() - 1.0)
+            zresult[i] += params.noiseAmplitude * (2.0 * rrSeries.rng.nextDouble() - 1.0)
         }
         return zresult
     }
diff --git a/Sources/ECGSynKit/ECGSynRRGenerator.swift b/Sources/ECGSynKit/ECGSynRRGenerator.swift
index dd07b15..2a916fe 100644
--- a/Sources/ECGSynKit/ECGSynRRGenerator.swift
+++ b/Sources/ECGSynKit/ECGSynRRGenerator.swift
@@ -68,7 +68,7 @@ public struct ECGSynRRGenerator: ~Copyable {
 
         fft.inverse(spectrum: spectrum, signal: signal)
 
-        var rr = signal.map { $0 * 1.0 / Double(nrr) }
+        var rr = signal.map { $0 * (1.0 / Double(nrr)) }
 
         let xstd = stdev(rr)
         let ratio = rrStd / xstd