diff --git a/slsReceiverSoftware/src/Fifo.cpp b/slsReceiverSoftware/src/Fifo.cpp
index 1bec44e12..6740c8ae2 100644
--- a/slsReceiverSoftware/src/Fifo.cpp
+++ b/slsReceiverSoftware/src/Fifo.cpp
@@ -81,7 +81,10 @@ void Fifo::DestroyFifos() {
     fifoStream = nullptr;
 }
 
-void Fifo::FreeAddress(char *&address) { fifoFree->push(address); }
+void Fifo::FreeAddress(char *&address) {
+    std::lock_guard<std::mutex> lock(fifoFreeMutex);
+    fifoFree->push(address);
+}
 
 void Fifo::GetNewAddress(char *&address) {
     int temp = fifoFree->getDataValue();
diff --git a/slsReceiverSoftware/src/Fifo.h b/slsReceiverSoftware/src/Fifo.h
index 729ce368b..fe9f3cf1e 100644
--- a/slsReceiverSoftware/src/Fifo.h
+++ b/slsReceiverSoftware/src/Fifo.h
@@ -16,6 +16,7 @@
 #include "sls/sls_detector_defs.h"
 
 #include <atomic>
+#include <mutex>
 
 namespace sls {
 
@@ -52,6 +53,9 @@ class Fifo : private virtual slsDetectorDefs {
     int fifoDepth;
     std::atomic<int> status_fifoBound;
     std::atomic<int> status_fifoFree;
+    /** fifoFree has several producers, CircularFifo allows only one.
+     * Aligned to avoid false sharing with the members above */
+    alignas(128) std::mutex fifoFreeMutex;
 };
 
 } // namespace sls