diff --git a/src/prim/prim.c b/src/prim/prim.c
index 83b7abc1..eec13c48 100644
--- a/src/prim/prim.c
+++ b/src/prim/prim.c
@@ -9,10 +9,10 @@ terms of the MIT license. A copy of the license can be found in the file
 // depending on the OS.
 
 #if defined(_WIN32)
-#include "prim-windows.c"  // VirtualAlloc (Windows)
+#include "windows/prim.c"  // VirtualAlloc (Windows)
 #elif defined(__wasi__)
 #define MI_USE_SBRK
-#include "prim-wasi.h"     // memory-grow or sbrk (Wasm)
+#include "wasi/prim.h"     // memory-grow or sbrk (Wasm)
 #else
-#include "prim-unix.c"     // mmap() (Linux, macOSX, BSD, Illumnos, Haiku, DragonFly, etc.)
+#include "unix/prim.c"     // mmap() (Linux, macOSX, BSD, Illumnos, Haiku, DragonFly, etc.)
 #endif
diff --git a/src/prim/prim-unix.c b/src/prim/unix/prim.c
similarity index 99%
rename from src/prim/prim-unix.c
rename to src/prim/unix/prim.c
index 997c0356..d1cd4301 100644
--- a/src/prim/prim-unix.c
+++ b/src/prim/unix/prim.c
@@ -5,6 +5,8 @@ terms of the MIT license. A copy of the license can be found in the file
 "LICENSE" at the root of this distribution.
 -----------------------------------------------------------------------------*/
 
+// This file is included in `src/prim/prim.c`
+
 #ifndef _DEFAULT_SOURCE
 #define _DEFAULT_SOURCE   // ensure mmap flags and syscall are defined
 #endif
@@ -21,7 +23,7 @@ terms of the MIT license. A copy of the license can be found in the file
 #include "mimalloc.h"
 #include "mimalloc-internal.h"
 #include "mimalloc-atomic.h"
-#include "prim.h"
+#include "../prim.h"
 
 #include <sys/mman.h>  // mmap
 #include <unistd.h>    // sysconf
diff --git a/src/prim/prim-wasi.c b/src/prim/wasi/prim.c
similarity index 99%
rename from src/prim/prim-wasi.c
rename to src/prim/wasi/prim.c
index f4d3be58..b8ac1a1b 100644
--- a/src/prim/prim-wasi.c
+++ b/src/prim/wasi/prim.c
@@ -5,10 +5,12 @@ terms of the MIT license. A copy of the license can be found in the file
 "LICENSE" at the root of this distribution.
 -----------------------------------------------------------------------------*/
 
+// This file is included in `src/prim/prim.c`
+
 #include "mimalloc.h"
 #include "mimalloc-internal.h"
 #include "mimalloc-atomic.h"
-#include "prim.h"
+#include "../prim.h"
 
 //---------------------------------------------
 // Initialize
diff --git a/src/prim/prim-windows.c b/src/prim/windows/prim.c
similarity index 99%
rename from src/prim/prim-windows.c
rename to src/prim/windows/prim.c
index 008b9fa4..2fa445a1 100644
--- a/src/prim/prim-windows.c
+++ b/src/prim/windows/prim.c
@@ -5,10 +5,12 @@ terms of the MIT license. A copy of the license can be found in the file
 "LICENSE" at the root of this distribution.
 -----------------------------------------------------------------------------*/
 
+// This file is included in `src/prim/prim.c`
+
 #include "mimalloc.h"
 #include "mimalloc-internal.h"
 #include "mimalloc-atomic.h"
-#include "prim.h"
+#include "../prim.h"
 #include <string.h>  // strerror
 #include <stdio.h>   // fputs, stderr