diff --git a/Python/thread.c b/Python/thread.c
index 63eeb1e..3a52e1e 100644
--- a/Python/thread.c
+++ b/Python/thread.c
@@ -172,7 +172,7 @@
     struct key *next;
 
     /* The thread id, according to PyThread_get_thread_ident(). */
-    long id;
+    unsigned long id;
 
     /* The key and its associated value. */
     int key;
@@ -208,7 +208,7 @@
 find_key(int set_value, int key, void *value)
 {
     struct key *p, *prev_p;
-    long id = PyThread_get_thread_ident();
+    unsigned long id = PyThread_get_thread_ident();
 
     if (!keymutex)
         return NULL;
@@ -312,7 +312,7 @@
 void
 PyThread_delete_key_value(int key)
 {
-    long id = PyThread_get_thread_ident();
+    unsigned long id = PyThread_get_thread_ident();
     struct key *p, **q;
 
     PyThread_acquire_lock(keymutex, 1);
@@ -338,7 +338,7 @@
 void
 PyThread_ReInitTLS(void)
 {
-    long id = PyThread_get_thread_ident();
+    unsigned long id = PyThread_get_thread_ident();
     struct key *p, **q;
 
     if (!keymutex)