diff --git a/src/audio_file.cc b/src/audio_file.cc
index d9001de..d4a507d 100644
--- a/src/audio_file.cc
+++ b/src/audio_file.cc
@@ -6,7 +6,6 @@
 #include "sound.h"
 
 #include <assert.h>
-#include <io.h>
 #include <stdio.h>
 #include <string.h>
 
@@ -100,7 +99,7 @@ int audioFileOpen(const char* fname, int flags, ...)
         audioFile->soundDecoder = soundDecoderInit(audioFileSoundDecoderReadHandler, audioFile->fileHandle, &(audioFile->field_14), &(audioFile->field_10), &(audioFile->fileSize));
         audioFile->fileSize *= 2;
     } else {
-        audioFile->fileSize = filelength(fileno(stream));
+        audioFile->fileSize = compat_filelength(fileno(stream));
     }
 
     audioFile->position = 0;
diff --git a/src/cache.cc b/src/cache.cc
index e6ed0b3..e2c77f3 100644
--- a/src/cache.cc
+++ b/src/cache.cc
@@ -5,6 +5,7 @@
 #include "sound.h"
 
 #include <limits.h>
+#include <stdlib.h> // qsort
 #include <stdio.h>
 #include <string.h>
 
diff --git a/src/dfile.cc b/src/dfile.cc
index 2332c46..9d71446 100644
--- a/src/dfile.cc
+++ b/src/dfile.cc
@@ -5,7 +5,6 @@
 #include <fpattern.h>
 
 #include <assert.h>
-#include <io.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -32,7 +31,7 @@ DBase* dbaseOpen(const char* filePath)
 
     // Get file size, and reposition stream to read footer, which contains two
     // 32-bits ints.
-    int fileSize = filelength(fileno(stream));
+    int fileSize = compat_filelength(fileno(stream));
     if (fseek(stream, fileSize - sizeof(int) * 2, SEEK_SET) != 0) {
         goto err;
     }
diff --git a/src/game.cc b/src/game.cc
index eeeb359..1cc632f 100644
--- a/src/game.cc
+++ b/src/game.cc
@@ -56,7 +56,12 @@
 #include "window_manager.h"
 #include "world_map.h"
 
+#ifdef _WIN32
 #include <io.h>
+#else
+#include <unistd.h> // access
+#endif
+
 #include <stdio.h>
 
 #define HELP_SCREEN_WIDTH (640)
diff --git a/src/platform_compat.cc b/src/platform_compat.cc
index 7429292..2b9623f 100644
--- a/src/platform_compat.cc
+++ b/src/platform_compat.cc
@@ -5,6 +5,13 @@
 
 #include <filesystem>
 
+#ifdef _WIN32
+#include <io.h>
+#include <stdio.h>
+#else
+#include <unistd.h>
+#endif
+
 int compat_stricmp(const char* string1, const char* string2)
 {
     return SDL_strcasecmp(string1, string2);
@@ -81,3 +88,12 @@ void compat_makepath(char* path, const char* drive, const char* dir, const char*
     strcpy(path, p.string().substr(0, COMPAT_MAX_PATH - 1).c_str());
 #endif
 }
+
+long compat_filelength(int fd)
+{
+    long originalOffset = lseek(fd, 0, SEEK_CUR);
+    lseek(fd, 0, SEEK_SET);
+    long filesize = lseek(fd, 0, SEEK_END);
+    lseek(fd, originalOffset, SEEK_SET);
+    return filesize;
+}
diff --git a/src/platform_compat.h b/src/platform_compat.h
index a46bfd7..1b63744 100644
--- a/src/platform_compat.h
+++ b/src/platform_compat.h
@@ -24,5 +24,6 @@ char* compat_strlwr(char* string);
 char* compat_itoa(int value, char* buffer, int radix);
 void compat_splitpath(const char* path, char* drive, char* dir, char* fname, char* ext);
 void compat_makepath(char* path, const char* drive, const char* dir, const char* fname, const char* ext);
+long compat_filelength(int fd);
 
 #endif /* PLATFORM_COMPAT_H */
diff --git a/src/sound.cc b/src/sound.cc
index 00ec98f..6718ccb 100644
--- a/src/sound.cc
+++ b/src/sound.cc
@@ -2,6 +2,7 @@
 
 #include "debug.h"
 #include "memory.h"
+#include "platform_compat.h"
 
 #include <io.h>
 #include <limits.h>
@@ -37,7 +38,7 @@ SoundFileIO gSoundDefaultFileIO = {
     write,
     lseek,
     tell,
-    filelength,
+    compat_filelength,
     -1,
 };
 
diff --git a/src/xfile.cc b/src/xfile.cc
index 5524b91..3a2f6e3 100644
--- a/src/xfile.cc
+++ b/src/xfile.cc
@@ -418,7 +418,7 @@ long xfileGetSize(XFile* stream)
         fileSize = 0;
         break;
     default:
-        fileSize = filelength(fileno(stream->file));
+        fileSize = compat_filelength(fileno(stream->file));
         break;
     }