diff --git a/libs/main/types/pisystemtime.cpp b/libs/main/types/pisystemtime.cpp
index cd99e88b..f41a4e2c 100644
--- a/libs/main/types/pisystemtime.cpp
+++ b/libs/main/types/pisystemtime.cpp
@@ -225,12 +225,18 @@ PISystemTime PITimeMeasurer::elapsed() const {
 // PISystemTime::Frequency
 
 PISystemTime PISystemTime::Frequency::toSystemTime() const {
-	if (value_hz <= 0.) return PISystemTime();
+	if (value_hz <= 0.) {
+		piCout << "[PISystemTime::Frequency] toSystemTime() warning: invalid hertz" << value_hz;
+		return PISystemTime();
+	}
 	return PISystemTime::fromSeconds(1. / value_hz);
 }
 
 
 PISystemTime::Frequency PISystemTime::Frequency::fromSystemTime(const PISystemTime & st) {
-	if (st == PISystemTime()) return Frequency();
+	if (st == PISystemTime()) {
+		piCout << "[PISystemTime::Frequency] fromSystemTime() warning: null frequency";
+		return Frequency();
+	}
 	return Frequency(1. / st.toSeconds());
 }