diff --git a/xmrstak/misc/telemetry.cpp b/xmrstak/misc/telemetry.cpp
index 5642f6b66779bfec21c105fd84fce853c00546f2..197da8ecaac4398bce23df354579e16afa8500a4 100644
--- a/xmrstak/misc/telemetry.cpp
+++ b/xmrstak/misc/telemetry.cpp
@@ -49,6 +49,7 @@ telemetry::telemetry(size_t iThd)
 
 double telemetry::calc_telemetry_data(size_t iLastMillisec, size_t iThread)
 {
+	std::unique_lock<std::mutex> lk(mtx);
 	uint64_t iTimeNow = get_timestamp_ms();
 
 	uint64_t iEarliestHashCnt = 0;
@@ -98,6 +99,7 @@ double telemetry::calc_telemetry_data(size_t iLastMillisec, size_t iThread)
 
 void telemetry::push_perf_value(size_t iThd, uint64_t iHashCount, uint64_t iTimestamp)
 {
+	std::unique_lock<std::mutex> lk(mtx);
 	size_t iTop = iBucketTop[iThd];
 	ppHashCounts[iThd][iTop] = iHashCount;
 	ppTimestamps[iThd][iTop] = iTimestamp;
diff --git a/xmrstak/misc/telemetry.hpp b/xmrstak/misc/telemetry.hpp
index 309fd6d06055f446737238565117005ea7d721ce..1813c00e6a07d41917ffe621d348a36be0ab8706 100644
--- a/xmrstak/misc/telemetry.hpp
+++ b/xmrstak/misc/telemetry.hpp
@@ -2,6 +2,7 @@
 
 #include <cstdint>
 #include <cstring>
+#include <mutex>
 
 namespace xmrstak
 {
@@ -14,6 +15,7 @@ public:
 	double calc_telemetry_data(size_t iLastMillisec, size_t iThread);
 
 private:
+	mutable std::mutex mtx;
 	constexpr static size_t iBucketSize = 2 << 11; //Power of 2 to simplify calculations
 	constexpr static size_t iBucketMask = iBucketSize - 1;
 	uint32_t* iBucketTop;