diff --git a/core/hw/mem/mem_watch.h b/core/hw/mem/mem_watch.h
index b91b76060..4d1be89ee 100644
--- a/core/hw/mem/mem_watch.h
+++ b/core/hw/mem/mem_watch.h
@@ -16,6 +16,7 @@
     You should have received a copy of the GNU General Public License
     along with Flycast.  If not, see <https://www.gnu.org/licenses/>.
 */
+#pragma once
 #include "types.h"
 #include "addrspace.h"
 #include "hw/aica/aica_if.h"
diff --git a/core/hw/sh4/dyna/ssa.h b/core/hw/sh4/dyna/ssa.h
index a2e34d920..68f84d558 100644
--- a/core/hw/sh4/dyna/ssa.h
+++ b/core/hw/sh4/dyna/ssa.h
@@ -18,6 +18,7 @@
     You should have received a copy of the GNU General Public License
     along with reicast.  If not, see <https://www.gnu.org/licenses/>.
  */
+#pragma once
 #include <cstdio>
 #include <set>
 #include <map>
diff --git a/core/hw/sh4/modules/wince.h b/core/hw/sh4/modules/wince.h
index 71f9c2d5c..3967488a9 100644
--- a/core/hw/sh4/modules/wince.h
+++ b/core/hw/sh4/modules/wince.h
@@ -16,6 +16,7 @@
     You should have received a copy of the GNU General Public License
     along with reicast.  If not, see <https://www.gnu.org/licenses/>.
  */
+#pragma once
 #ifdef TRACE_WINCE_SYSCALLS
 #include "hw/sh4/sh4_sched.h"
 
diff --git a/core/linux-dist/evdev_gamepad.h b/core/linux-dist/evdev_gamepad.h
index cfbe27355..263868453 100644
--- a/core/linux-dist/evdev_gamepad.h
+++ b/core/linux-dist/evdev_gamepad.h
@@ -1,3 +1,4 @@
+#pragma once
 #include "evdev.h"
 #include "input/gamepad_device.h"
 #include "oslib/oslib.h"
diff --git a/core/log/StringUtil.h b/core/log/StringUtil.h
index 15cd9a5f0..a9b1625eb 100644
--- a/core/log/StringUtil.h
+++ b/core/log/StringUtil.h
@@ -1,3 +1,4 @@
+#pragma once
 #include <locale>
 
 #ifdef _WIN32
diff --git a/core/lua/lua.h b/core/lua/lua.h
index 28806c57b..4d190057c 100644
--- a/core/lua/lua.h
+++ b/core/lua/lua.h
@@ -16,6 +16,7 @@
     You should have received a copy of the GNU General Public License
     along with Flycast.  If not, see <https://www.gnu.org/licenses/>.
 */
+#pragma once
 #include "build.h"
 #include <string>
 
diff --git a/core/network/net_serial_maxspeed.h b/core/network/net_serial_maxspeed.h
index 3214a4f76..c564919a5 100644
--- a/core/network/net_serial_maxspeed.h
+++ b/core/network/net_serial_maxspeed.h
@@ -16,6 +16,7 @@
     You should have received a copy of the GNU General Public License
     along with Flycast.  If not, see <https://www.gnu.org/licenses/>.
  */
+#pragma once
 #include "hw/sh4/modules/modules.h"
 #include "net_platform.h"
 #include "cfg/option.h"
diff --git a/core/network/null_modem.h b/core/network/null_modem.h
index 69314b09c..440ee589a 100644
--- a/core/network/null_modem.h
+++ b/core/network/null_modem.h
@@ -16,6 +16,7 @@
     You should have received a copy of the GNU General Public License
     along with Flycast.  If not, see <https://www.gnu.org/licenses/>.
  */
+#pragma once
 #include "hw/sh4/modules/modules.h"
 #include "net_platform.h"
 #include "cfg/option.h"
diff --git a/core/oslib/virtmem.h b/core/oslib/virtmem.h
index be2ad7c2f..79b774d95 100644
--- a/core/oslib/virtmem.h
+++ b/core/oslib/virtmem.h
@@ -1,3 +1,4 @@
+#pragma once
 #include "types.h"
 
 namespace virtmem
diff --git a/core/rend/boxart/gamesdb.h b/core/rend/boxart/gamesdb.h
index bf9998bfc..2433681f3 100644
--- a/core/rend/boxart/gamesdb.h
+++ b/core/rend/boxart/gamesdb.h
@@ -16,6 +16,7 @@
     You should have received a copy of the GNU General Public License
     along with Flycast.  If not, see <https://www.gnu.org/licenses/>.
  */
+#pragma once
 #include "scraper.h"
 #include "json.hpp"
 
diff --git a/core/rend/boxart/http_client.h b/core/rend/boxart/http_client.h
index 2b44aad1b..846abc126 100644
--- a/core/rend/boxart/http_client.h
+++ b/core/rend/boxart/http_client.h
@@ -16,6 +16,7 @@
     You should have received a copy of the GNU General Public License
     along with Flycast.  If not, see <https://www.gnu.org/licenses/>.
  */
+#pragma once
 #include <string>
 #include <vector>
 #include <cctype>
diff --git a/core/rend/vulkan/compiler.h b/core/rend/vulkan/compiler.h
index 2025d7397..cc4d7249d 100644
--- a/core/rend/vulkan/compiler.h
+++ b/core/rend/vulkan/compiler.h
@@ -18,6 +18,7 @@
     You should have received a copy of the GNU General Public License
     along with Flycast.  If not, see <https://www.gnu.org/licenses/>.
 */
+#pragma once
 #include "vulkan.h"
 
 class ShaderCompiler
diff --git a/core/rend/vulkan/vulkan_renderer.h b/core/rend/vulkan/vulkan_renderer.h
index d2119ef82..4c33919e0 100644
--- a/core/rend/vulkan/vulkan_renderer.h
+++ b/core/rend/vulkan/vulkan_renderer.h
@@ -16,6 +16,7 @@
     You should have received a copy of the GNU General Public License
     along with Flycast.  If not, see <https://www.gnu.org/licenses/>.
 */
+#pragma once
 #include "vulkan.h"
 #include "hw/pvr/Renderer_if.h"
 #include "hw/pvr/ta.h"
diff --git a/core/sdl/sdl_gamepad.h b/core/sdl/sdl_gamepad.h
index 05e0a450c..f62ea604a 100644
--- a/core/sdl/sdl_gamepad.h
+++ b/core/sdl/sdl_gamepad.h
@@ -1,3 +1,4 @@
+#pragma once
 #include "input/gamepad_device.h"
 #include "input/mouse.h"
 #include "oslib/oslib.h"
diff --git a/core/windows/rawinput.h b/core/windows/rawinput.h
index 1577264ac..58c8e6a89 100644
--- a/core/windows/rawinput.h
+++ b/core/windows/rawinput.h
@@ -16,6 +16,7 @@
     You should have received a copy of the GNU General Public License
     along with Flycast.  If not, see <https://www.gnu.org/licenses/>.
 */
+#pragma once
 #include "build.h"
 #ifndef TARGET_UWP
 #include "input/gamepad_device.h"