diff --git a/runtime/include/psx_bss.h b/runtime/include/psx_bss.h
index 783286e3..d903df9c 100644
--- a/runtime/include/psx_bss.h
+++ b/runtime/include/psx_bss.h
@@ -3,11 +3,16 @@
  * MinGW + LTO has been observed to place multi‑MiB uninitialized globals into
  * .rdata as literal zeros, bloating release .exe size by ~100+ MiB (e.g.
  * g_fntrace_ring). Explicit .bss placement keeps them RAM-only on disk.
+ *
+ * Mach-O requires "segment,section" (not ELF ".bss"); Apple Clang rejects
+ * section(".bss") at compile time.
  */
 #ifndef PSXRECOMP_PSX_BSS_H
 #define PSXRECOMP_PSX_BSS_H
 
-#if defined(__GNUC__) || defined(__clang__)
+#if defined(__APPLE__)
+#define PSX_BSS __attribute__((section("__DATA,__bss")))
+#elif defined(__GNUC__) || defined(__clang__)
 #define PSX_BSS __attribute__((section(".bss")))
 #elif defined(_MSC_VER)
 /* MSVC already puts uninitialized globals in .bss by default. */