diff --git a/src/thermo.cpp b/src/thermo.cpp
index d7a00fd14c..35b5016118 100644
--- a/src/thermo.cpp
+++ b/src/thermo.cpp
@@ -48,7 +48,6 @@
 
 #include <cmath>
 #include <cstring>
-#include <mutex>
 #include <stdexcept>
 
 using namespace LAMMPS_NS;
diff --git a/src/thermo.h b/src/thermo.h
index b5934f48b1..f5466e70cd 100644
--- a/src/thermo.h
+++ b/src/thermo.h
@@ -16,10 +16,7 @@
 
 #include "pointers.h"
 #include <map>
-
-namespace std {
-class mutex;
-}
+#include <mutex>
 
 namespace LAMMPS_NS {