diff --git a/rtengine/dfmanager.h b/rtengine/dfmanager.h
index 2e55c3c22..541981492 100644
--- a/rtengine/dfmanager.h
+++ b/rtengine/dfmanager.h
@@ -16,10 +16,14 @@
  *  You should have received a copy of the GNU General Public License
  *  along with RawTherapee.  If not, see <http://www.gnu.org/licenses/>.
  */
-#include <string>
-#include <glibmm/ustring.h>
-#include <map>
+#pragma once
+
 #include <cmath>
+#include <map>
+#include <string>
+
+#include <glibmm/ustring.h>
+
 #include "pixelsmap.h"
 #include "rawimage.h"
 
diff --git a/rtengine/ffmanager.h b/rtengine/ffmanager.h
index 9068216ef..43fb2f368 100644
--- a/rtengine/ffmanager.h
+++ b/rtengine/ffmanager.h
@@ -16,10 +16,14 @@
  *  You should have received a copy of the GNU General Public License
  *  along with RawTherapee.  If not, see <http://www.gnu.org/licenses/>.
  */
-#include <string>
-#include <glibmm/ustring.h>
-#include <map>
+#pragma once
+
 #include <cmath>
+#include <map>
+#include <string>
+
+#include <glibmm/ustring.h>
+
 #include "rawimage.h"
 
 namespace rtengine
diff --git a/rtengine/iccjpeg.h b/rtengine/iccjpeg.h
index ce715948d..5197d1602 100644
--- a/rtengine/iccjpeg.h
+++ b/rtengine/iccjpeg.h
@@ -15,6 +15,7 @@
  * with ICC profiles exceeding 64K bytes in size.  See iccprofile.c
  * for details.
  */
+#pragma once
 
 #include <cstdio>       /* needed to define "FILE", "NULL" */
 #include "jpeglib.h"