diff --git a/lib/colvars/colvarmodule.cpp b/lib/colvars/colvarmodule.cpp
index c9e2d14116..dc6242c5bc 100644
--- a/lib/colvars/colvarmodule.cpp
+++ b/lib/colvars/colvarmodule.cpp
@@ -8,7 +8,7 @@
 // Colvars repository at GitHub.
 
 #include <sstream>
-#include <string.h>
+#include <cstring>
 
 #include "colvarmodule.h"
 #include "colvarparse.h"
diff --git a/lib/colvars/colvarproxy.cpp b/lib/colvars/colvarproxy.cpp
index c2992c309c..86338dfd1b 100644
--- a/lib/colvars/colvarproxy.cpp
+++ b/lib/colvars/colvarproxy.cpp
@@ -8,7 +8,7 @@
 // Colvars repository at GitHub.
 
 #include <sstream>
-#include <string.h>
+#include <cstring>
 
 #if defined(_OPENMP)
 #include <omp.h>
diff --git a/lib/colvars/colvarscript.cpp b/lib/colvars/colvarscript.cpp
index 0977496b9e..a55e4c65d9 100644
--- a/lib/colvars/colvarscript.cpp
+++ b/lib/colvars/colvarscript.cpp
@@ -8,8 +8,7 @@
 // Colvars repository at GitHub.
 
 #include <cstdlib>
-#include <stdlib.h>
-#include <string.h>
+#include <cstring>
 
 #define COLVARSCRIPT_CPP
 #include "colvarscript.h"
diff --git a/lib/colvars/colvartypes.cpp b/lib/colvars/colvartypes.cpp
index b604606d46..2b45d77e07 100644
--- a/lib/colvars/colvartypes.cpp
+++ b/lib/colvars/colvartypes.cpp
@@ -7,8 +7,8 @@
 // If you wish to distribute your changes, please submit them to the
 // Colvars repository at GitHub.
 
-#include <stdlib.h>
-#include <string.h>
+#include <cstdlib>
+#include <cstring>
 
 #include "colvarmodule.h"
 #include "colvartypes.h"