diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index 8fbaf22..f131d7a 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -44,6 +44,11 @@
 /* Is this the main thread? */
 #define PTHREAD_ATTR_FLAG_MAIN_THREAD 0x80000000
 
+struct pthread_key_data_t {
+  uintptr_t seq; // Use uintptr_t just for alignment, as we use pointer below.
+  void* data;
+};
+
 struct pthread_internal_t {
   struct pthread_internal_t* next;
   struct pthread_internal_t* prev;
@@ -86,6 +91,8 @@
 
   void* tls[BIONIC_TLS_SLOTS];
 
+  pthread_key_data_t key_data[BIONIC_PTHREAD_KEY_COUNT];
+
   /*
    * The dynamic linker implements dlerror(3), which makes it hard for us to implement this
    * per-thread buffer by simply using malloc(3) and free(3).