diff --git a/internal/vfs/tests/mptest/testdata/main.c b/internal/vfs/tests/mptest/testdata/main.c
index 028247d..a54fe90 100644
--- a/internal/vfs/tests/mptest/testdata/main.c
+++ b/internal/vfs/tests/mptest/testdata/main.c
@@ -1,11 +1,12 @@
 #include <stdbool.h>
 #include <stddef.h>
 
+// Configuration
 #include "sqlite_cfg.h"
-//
+// Amalgamation
 #include "sqlite3.c"
-//
-#include "os.c"
+// VFS
+#include "vfs.c"
 
 sqlite3_destructor_type malloc_destructor = &free;
 size_t sqlite3_interrupt_offset = offsetof(sqlite3, u1.isInterrupted);
diff --git a/internal/vfs/tests/speedtest1/testdata/main.c b/internal/vfs/tests/speedtest1/testdata/main.c
index 64831ac..44b6eee 100644
--- a/internal/vfs/tests/speedtest1/testdata/main.c
+++ b/internal/vfs/tests/speedtest1/testdata/main.c
@@ -1,11 +1,12 @@
 #include <stdbool.h>
 #include <stddef.h>
 
+// Configuration
 #include "sqlite_cfg.h"
-//
+// Amalgamation
 #include "sqlite3.c"
-//
-#include "os.c"
+// VFS
+#include "vfs.c"
 
 sqlite3_destructor_type malloc_destructor = &free;
 size_t sqlite3_interrupt_offset = offsetof(sqlite3, u1.isInterrupted);
diff --git a/sqlite3/main.c b/sqlite3/main.c
index 4c9dbc7..ef90dfb 100644
--- a/sqlite3/main.c
+++ b/sqlite3/main.c
@@ -1,12 +1,13 @@
 #include <stdbool.h>
 #include <stddef.h>
 
+// Configuration
 #include "sqlite_cfg.h"
-//
+// Amalgamation
 #include "sqlite3.c"
-//
-#include "os.c"
-//
+// VFS
+#include "vfs.c"
+// Extensions
 #include "ext/base64.c"
 #include "ext/decimal.c"
 #include "ext/regexp.c"
diff --git a/sqlite3/sqlite_cfg.h b/sqlite3/sqlite_cfg.h
index 8f445fb..34fd489 100644
--- a/sqlite3/sqlite_cfg.h
+++ b/sqlite3/sqlite_cfg.h
@@ -40,7 +40,7 @@
 #define SQLITE_DEFAULT_LOCKING_MODE 1
 #endif
 
-// Recommended Extensions
+// Amalgamated Extensions
 
 #define SQLITE_ENABLE_MATH_FUNCTIONS 1
 #define SQLITE_ENABLE_JSON1 1
@@ -55,5 +55,13 @@
 // #define SQLITE_ENABLE_SESSION
 // #define SQLITE_ENABLE_PREUPDATE_HOOK
 
-// Implemented in os.c.
+// https://stackoverflow.com/a/50616684
+#define SECOND(...) SECOND_I(__VA_ARGS__,,)
+#define SECOND_I(A,B,...) B
+#define GLUE(A,B) GLUE_I(A,B)
+#define GLUE_I(A,B) A##B
+#define REPLACE_DEFAULT(a, prefix) SECOND(GLUE(prefix, __LINE__), a)
+#define REPLACE_AT_LINE(a) ,a
+
+// Implemented in vfs.c.
 int localtime_s(struct tm *const pTm, time_t const *const pTime);
\ No newline at end of file
diff --git a/sqlite3/os.c b/sqlite3/vfs.c
similarity index 100%
rename from sqlite3/os.c
rename to sqlite3/vfs.c