diff --git a/src/gameconfigfile.cpp b/src/gameconfigfile.cpp
index 3bd34fd15..ee52313ce 100644
--- a/src/gameconfigfile.cpp
+++ b/src/gameconfigfile.cpp
@@ -47,6 +47,9 @@
 #include "doomstat.h"
 #include "gi.h"
 #include "d_main.h"
+#if !defined _MSC_VER && !defined __APPLE__
+#include "i_system.h"  // for SHARE_DIR
+#endif // !_MSC_VER && !__APPLE__
 
 EXTERN_CVAR (Bool, con_centernotify)
 EXTERN_CVAR (Int, msg0color)
diff --git a/src/posix/cocoa/i_video.mm b/src/posix/cocoa/i_video.mm
index 7b20907f2..0c1abb883 100644
--- a/src/posix/cocoa/i_video.mm
+++ b/src/posix/cocoa/i_video.mm
@@ -39,6 +39,7 @@
 #include "c_dispatch.h"
 #include "doomstat.h"
 #include "hardware.h"
+#include "i_system.h"
 #include "m_argv.h"
 #include "m_png.h"
 #include "r_renderer.h"
diff --git a/src/posix/sdl/hardware.cpp b/src/posix/sdl/hardware.cpp
index a26536538..61d36abf0 100644
--- a/src/posix/sdl/hardware.cpp
+++ b/src/posix/sdl/hardware.cpp
@@ -35,6 +35,7 @@
 #include <SDL.h>
 #include <signal.h>
 
+#include "i_system.h"
 #include "hardware.h"
 #include "c_dispatch.h"
 #include "v_text.h"
diff --git a/src/posix/sdl/i_input.cpp b/src/posix/sdl/i_input.cpp
index cc40b4fde..70a636dc6 100644
--- a/src/posix/sdl/i_input.cpp
+++ b/src/posix/sdl/i_input.cpp
@@ -44,6 +44,7 @@
 #include "c_dispatch.h"
 #include "dikeys.h"
 #include "events.h"
+#include "g_game.h"
 
 static void I_CheckGUICapture ();
 static void I_CheckNativeMouse ();
diff --git a/src/posix/sdl/i_main.cpp b/src/posix/sdl/i_main.cpp
index 05b0e6425..4ea48c401 100644
--- a/src/posix/sdl/i_main.cpp
+++ b/src/posix/sdl/i_main.cpp
@@ -54,6 +54,8 @@
 #include "doomstat.h"
 #include "vm.h"
 #include "doomerrors.h"
+#include "i_system.h"
+#include "g_game.h"
 
 // MACROS ------------------------------------------------------------------
 
diff --git a/src/posix/sdl/i_system.cpp b/src/posix/sdl/i_system.cpp
index 8b73d2f14..9303fc6eb 100644
--- a/src/posix/sdl/i_system.cpp
+++ b/src/posix/sdl/i_system.cpp
@@ -19,7 +19,9 @@
 //-----------------------------------------------------------------------------
 //
 
+#include "i_system.h"
 
+#include <dirent.h>
 #include <sys/wait.h>
 #include <stdlib.h>
 #include <stdio.h>
diff --git a/src/scripting/decorate/thingdef_parse.cpp b/src/scripting/decorate/thingdef_parse.cpp
index 68ab70cac..6bc8074f3 100644
--- a/src/scripting/decorate/thingdef_parse.cpp
+++ b/src/scripting/decorate/thingdef_parse.cpp
@@ -48,6 +48,9 @@
 #include "v_text.h"
 #include "m_argv.h"
 #include "v_video.h"
+#ifndef _MSC_VER
+#include "i_system.h"  // for strlwr()
+#endif // !_MSC_VER
 
 void ParseOldDecoration(FScanner &sc, EDefinitionType def, PNamespace *ns);
 EXTERN_CVAR(Bool, strictdecorate);
diff --git a/src/scripting/decorate/thingdef_states.cpp b/src/scripting/decorate/thingdef_states.cpp
index d03069775..cede46bdd 100644
--- a/src/scripting/decorate/thingdef_states.cpp
+++ b/src/scripting/decorate/thingdef_states.cpp
@@ -44,6 +44,9 @@
 #include "p_local.h"
 #include "thingdef.h"
 #include "backend/codegen.h"
+#ifndef _MSC_VER
+#include "i_system.h"  // for strlwr()
+#endif // !_MSC_VER
 
 //==========================================================================
 //***
diff --git a/src/scripting/vm/jit_runtime.cpp b/src/scripting/vm/jit_runtime.cpp
index 5ef0760d6..f72402404 100644
--- a/src/scripting/vm/jit_runtime.cpp
+++ b/src/scripting/vm/jit_runtime.cpp
@@ -9,6 +9,7 @@
 #include <cxxabi.h>
 #include <cstring>
 #include <cstdlib>
+#include <memory>
 #endif
 
 struct JitFuncInfo
diff --git a/src/utility/cmdlib.cpp b/src/utility/cmdlib.cpp
index 7a7436c19..2ed0eefe9 100644
--- a/src/utility/cmdlib.cpp
+++ b/src/utility/cmdlib.cpp
@@ -26,6 +26,7 @@
 #include <direct.h>
 #include <io.h>
 #else
+#include <dirent.h>
 #include <unistd.h>
 #include <sys/types.h>
 #include <pwd.h>