diff --git a/src/fileio_func.h b/src/fileio_func.h
--- a/src/fileio_func.h
+++ b/src/fileio_func.h
@@ -57,6 +57,7 @@ char *FioAppendDirectory(char *buf, size
 char *FioGetDirectory(char *buf, size_t buflen, Subdirectory subdir);
 
 void SanitizeFilename(char *filename);
+void AppendPathSeparator(char *buf, size_t buflen);
 void DeterminePaths(const char *exe);
 void *ReadFileToMem(const char *filename, size_t *lenp, size_t maxsize);
 bool FileExists(const char *filename);