diff --git a/libc/private/bionic_tls.h b/libc/private/bionic_tls.h
index a626d21..f661ccf 100644
--- a/libc/private/bionic_tls.h
+++ b/libc/private/bionic_tls.h
@@ -43,24 +43,19 @@
  ** pre-allocated slot directly for performance reason).
  **/
 
-/* maximum number of elements in the TLS array */
+/* Maximum number of elements in the TLS array. */
 #define BIONIC_TLS_SLOTS            64
 
-/* note that slot 0, called TLS_SLOT_SELF must point to itself.
- * this is required to implement thread-local storage with the x86
- * Linux kernel, that reads the TLS from fs:[0], where 'fs' is a
- * thread-specific segment descriptor...
- */
-
-/* Well-known TLS slots. */
-#define TLS_SLOT_SELF               0
+/* Well-known TLS slots. What data goes in which slot is arbitrary unless otherwise noted. */
+#define TLS_SLOT_SELF               0  /* The kernel requires this specific slot for x86. */
 #define TLS_SLOT_THREAD_ID          1
 #define TLS_SLOT_ERRNO              2
 
 #define TLS_SLOT_OPENGL_API         3
 #define TLS_SLOT_OPENGL             4
 
-#define TLS_SLOT_DLERROR            5
+#define TLS_SLOT_STACK_GUARD        5  /* GCC requires this specific slot for x86. */
+#define TLS_SLOT_DLERROR            6
 
 #define TLS_SLOT_MAX_WELL_KNOWN     TLS_SLOT_DLERROR