diff --git a/src/i_flickstick.c b/src/i_flickstick.c
index 0edbff85c..745afc646 100644
--- a/src/i_flickstick.c
+++ b/src/i_flickstick.c
@@ -25,10 +25,11 @@
 //
 //----------------------------------------------------------------------------
 
-#include "g_game.h"
+#include <string.h>
+
+#include "doomstat.h"
 #include "i_flickstick.h"
 #include "i_gamepad.h"
-#include "i_input.h"
 #include "m_config.h"
 
 #define MAX_F 0.999999f
diff --git a/src/i_gamepad.h b/src/i_gamepad.h
index ea2fad042..b3cccc9be 100644
--- a/src/i_gamepad.h
+++ b/src/i_gamepad.h
@@ -17,6 +17,8 @@
 #ifndef __I_GAMEPAD__
 #define __I_GAMEPAD__
 
+#include <math.h>
+
 #include "d_event.h"
 #include "doomkeys.h"
 
diff --git a/src/i_video.c b/src/i_video.c
index 88908c0e2..09068ce96 100644
--- a/src/i_video.c
+++ b/src/i_video.c
@@ -26,6 +26,7 @@
 #include <SDL3/SDL.h>
 
 #include <limits.h>
+#include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
 
diff --git a/src/st_stuff.c b/src/st_stuff.c
index 2003d7829..e4f2c9854 100644
--- a/src/st_stuff.c
+++ b/src/st_stuff.c
@@ -21,6 +21,7 @@
 //-----------------------------------------------------------------------------
 
 #include <stdlib.h>
+#include <math.h>
 
 #include "am_map.h"
 #include "d_event.h"
diff --git a/textscreen/txt_fileselect.c b/textscreen/txt_fileselect.c
index 858c2c178..1e0f080a2 100644
--- a/textscreen/txt_fileselect.c
+++ b/textscreen/txt_fileselect.c
@@ -15,6 +15,7 @@
 // Routines for selecting files.
 //
 
+#include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>