diff --git a/lib/libc/gen/tls.c b/lib/libc/gen/tls.c
--- a/lib/libc/gen/tls.c
+++ b/lib/libc/gen/tls.c
@@ -72,11 +72,14 @@
 void *__libc_allocate_tls(void *oldtls, size_t tcbsize, size_t tcbalign);
 void __libc_free_tls(void *tls, size_t tcbsize, size_t tcbalign);
 
-#if defined(__amd64__)
+#if defined(__amd64__) || defined(__aarch64__) || defined(__riscv)
 #define TLS_TCB_ALIGN 16
-#elif defined(__aarch64__) || defined(__arm__) || defined(__i386__) || \
-    defined(__mips__) || defined(__powerpc__) || defined(__riscv)
-#define TLS_TCB_ALIGN sizeof(void *)
+#elif defined(__arm__) || defined(__mips__)
+#define TLS_TCB_ALIGN 8
+#elif defined(__powerpc__)
+#define TLS_TCB_ALIGN TLS_TCB_SIZE
+#elif defined(__i386__)
+#define TLS_TCB_ALIGN 4
 #else
 #error TLS_TCB_ALIGN undefined for target architecture
 #endif