diff --git a/src/d_loop.h b/src/d_loop.h
index f8538f0bb1..c154be3a64 100644
--- a/src/d_loop.h
+++ b/src/d_loop.h
@@ -20,6 +20,8 @@
 #define __D_LOOP__
 
 #include "net_defs.h"
+#include "m_fixed.h"
+
 
 // Callback function invoked while waiting for the netgame to start.
 // The callback is invoked when new players are ready. The callback
@@ -84,5 +86,11 @@ boolean D_NonVanillaRecord(boolean conditional, const char *feature);
 boolean D_NonVanillaPlayback(boolean conditional, int lumpnum,
                              const char *feature);
 
+void D_ReceiveTic(ticcmd_t *ticcmds, boolean *playeringame);
+
+
+extern fixed_t offsetms;
+
+
 #endif
 
diff --git a/src/deh_defs.h b/src/deh_defs.h
index 88c1e91f00..58b61e7cc1 100644
--- a/src/deh_defs.h
+++ b/src/deh_defs.h
@@ -58,6 +58,27 @@ struct deh_section_s
 extern deh_section_t *deh_section_types[];
 extern const char *deh_signatures[];
 
+// deh_ammo.c:
+extern deh_section_t deh_section_ammo;
+// deh_cheat.c:
+extern deh_section_t deh_section_cheat;
+// deh_frame.c:
+extern deh_section_t deh_section_frame;
+// deh_misc.c:
+extern deh_section_t deh_section_misc;
+// deh_ptr.c:
+extern deh_section_t deh_section_pointer;
+// deh_sound.c
+extern deh_section_t deh_section_sound;
+// deh_text.c:
+extern deh_section_t deh_section_text;
+// deh_thing.c:
+extern deh_section_t deh_section_thing;
+// deh_weapon.c:
+extern deh_section_t deh_section_weapon;
+// deh_bexstr.c:
+extern deh_section_t deh_section_bexstr;
+
 
 #endif /* #ifndef DEH_DEFS_H */
 
diff --git a/src/doom/deh_doom.c b/src/doom/deh_doom.c
index b13cc03f0f..b7ff04a738 100644
--- a/src/doom/deh_doom.c
+++ b/src/doom/deh_doom.c
@@ -26,26 +26,6 @@ const char *deh_signatures[] =
     NULL
 };
 
-// deh_ammo.c:
-extern deh_section_t deh_section_ammo;
-// deh_cheat.c:
-extern deh_section_t deh_section_cheat;
-// deh_frame.c:
-extern deh_section_t deh_section_frame;
-// deh_misc.c:
-extern deh_section_t deh_section_misc;
-// deh_ptr.c:
-extern deh_section_t deh_section_pointer;
-// deh_sound.c
-extern deh_section_t deh_section_sound;
-// deh_text.c:
-extern deh_section_t deh_section_text;
-// deh_thing.c:
-extern deh_section_t deh_section_thing;
-// deh_weapon.c:
-extern deh_section_t deh_section_weapon;
-// deh_bexstr.c:
-extern deh_section_t deh_section_bexstr;
 
 //
 // List of section types:
diff --git a/src/doom/m_menu.c b/src/doom/m_menu.c
index bf46b9086a..bccf0d0494 100644
--- a/src/doom/m_menu.c
+++ b/src/doom/m_menu.c
@@ -1899,7 +1899,6 @@ void M_StartControlPanel (void)
 
 static void M_DrawOPLDev(void)
 {
-    extern void I_OPL_DevMessages(char *, size_t);
     char debug[1024];
     char *curr, *p;
     int line;
diff --git a/src/heretic/deh_htic.c b/src/heretic/deh_htic.c
index c3aca3474c..0fe638b8ee 100644
--- a/src/heretic/deh_htic.c
+++ b/src/heretic/deh_htic.c
@@ -41,20 +41,8 @@ static const char *hhe_versions[] =
 
 deh_hhe_version_t deh_hhe_version = deh_hhe_1_0;
 
-// deh_ammo.c:
-extern deh_section_t deh_section_ammo;
-// deh_frame.c:
-extern deh_section_t deh_section_frame;
-// deh_ptr.c:
-extern deh_section_t deh_section_pointer;
-// deh_sound.c
-extern deh_section_t deh_section_sound;
 // deh_htext.c:
 extern deh_section_t deh_section_heretic_text;
-// deh_thing.c:
-extern deh_section_t deh_section_thing;
-// deh_weapon.c:
-extern deh_section_t deh_section_weapon;
 
 //
 // List of section types:
diff --git a/src/i_input.h b/src/i_input.h
index 8e3b2f1fa4..0dda76d073 100644
--- a/src/i_input.h
+++ b/src/i_input.h
@@ -22,6 +22,9 @@
 
 #include "doomtype.h"
 
+#include "SDL.h"
+
+
 #define MAX_MOUSE_BUTTONS 8
 
 extern float mouse_acceleration;
@@ -39,4 +42,8 @@ void I_StartTextInput(int x1, int y1, int x2, int y2);
 // (if one is used).
 void I_StopTextInput(void);
 
+void I_HandleKeyboardEvent(SDL_Event *sdlevent);
+void I_HandleMouseEvent(SDL_Event *sdlevent);
+
+
 #endif
diff --git a/src/i_sound.h b/src/i_sound.h
index b8aaf591c8..7a416231ce 100644
--- a/src/i_sound.h
+++ b/src/i_sound.h
@@ -248,6 +248,8 @@ typedef enum {
 } opl_driver_ver_t;
 
 void I_SetOPLDriverVer(opl_driver_ver_t ver);
+void I_OPL_DevMessages(char *, size_t);
+
 
 #ifdef _WIN32
 extern char *winmm_midi_device;
diff --git a/src/i_video.c b/src/i_video.c
index f1c67e6700..581b018197 100644
--- a/src/i_video.c
+++ b/src/i_video.c
@@ -415,8 +415,6 @@ static void I_ToggleFullScreen(void)
 
 void I_GetEvent(void)
 {
-    extern void I_HandleKeyboardEvent(SDL_Event *sdlevent);
-    extern void I_HandleMouseEvent(SDL_Event *sdlevent);
     SDL_Event sdlevent;
 
     SDL_PumpEvents();
diff --git a/src/i_video.h b/src/i_video.h
index 99375ef204..83ab96d5b4 100644
--- a/src/i_video.h
+++ b/src/i_video.h
@@ -95,10 +95,15 @@ extern int integer_scaling;
 extern int vga_porch_flash;
 extern int force_software_renderer;
 
+extern int png_screenshots;
+
 extern char *window_position;
 void I_GetWindowPosition(int *x, int *y, int w, int h);
 
 // Joystic/gamepad hysteresis
 extern unsigned int joywait;
 
+extern int usemouse;
+
+
 #endif
diff --git a/src/net_client.c b/src/net_client.c
index 3799b0e13e..19b720fa6a 100644
--- a/src/net_client.c
+++ b/src/net_client.c
@@ -23,6 +23,7 @@
 #include "doomtype.h"
 #include "deh_main.h"
 #include "deh_str.h"
+#include "d_loop.h"
 #include "i_system.h"
 #include "i_timer.h"
 #include "m_argv.h"
@@ -42,7 +43,6 @@
 #include "w_checksum.h"
 #include "w_wad.h"
 
-extern void D_ReceiveTic(ticcmd_t *ticcmds, boolean *playeringame);
 
 typedef enum
 {
@@ -99,7 +99,6 @@ typedef struct
     net_ticdiff_t cmd;
 } net_server_send_t;
 
-extern fixed_t offsetms;
 
 static net_connection_t client_connection;
 static net_clientstate_t client_state;
diff --git a/src/strife/deh_strife.c b/src/strife/deh_strife.c
index 231045b194..76cb496c16 100644
--- a/src/strife/deh_strife.c
+++ b/src/strife/deh_strife.c
@@ -26,24 +26,6 @@ const char *deh_signatures[] =
     NULL
 };
 
-// deh_ammo.c:
-extern deh_section_t deh_section_ammo;
-// deh_cheat.c:
-extern deh_section_t deh_section_cheat;
-// deh_frame.c:
-extern deh_section_t deh_section_frame;
-// deh_misc.c:
-extern deh_section_t deh_section_misc;
-// deh_ptr.c:
-extern deh_section_t deh_section_pointer;
-// deh_sound.c
-extern deh_section_t deh_section_sound;
-// deh_text.c:
-extern deh_section_t deh_section_text;
-// deh_thing.c:
-extern deh_section_t deh_section_thing;
-// deh_weapon.c:
-extern deh_section_t deh_section_weapon;
 
 //
 // List of section types:
diff --git a/src/v_video.c b/src/v_video.c
index 060f7e16f9..c35f259f40 100644
--- a/src/v_video.c
+++ b/src/v_video.c
@@ -841,7 +841,6 @@ void V_ScreenShot(const char *format)
     // find a file name to save it to
 
 #ifdef HAVE_LIBPNG
-    extern int png_screenshots;
     if (png_screenshots)
     {
         ext = "png";
@@ -986,7 +985,6 @@ static void DrawNonAcceleratingBox(int speed)
 
 void V_DrawMouseSpeedBox(int speed)
 {
-    extern int usemouse;
     int bgcolor, bordercolor, black;
 
     // If the mouse is turned off, don't draw the box at all.