diff -urp src.old/winsup/cygwin/thread.cc src/winsup/cygwin/thread.cc
--- src.old/winsup/cygwin/thread.cc	Fri Aug 16 12:52:02 2002
+++ src/winsup/cygwin/thread.cc	Fri Aug 16 13:14:49 2002
@@ -1020,16 +1020,27 @@ pthread_key::~pthread_key ()
 int
 pthread_key::set (const void *value)
 {
-  /*the OS function doesn't perform error checking */
-  TlsSetValue (dwTlsIndex, (void *) value);
+  if (dwTlsIndex == TLS_OUT_OF_INDEXES ||
+      !TlsSetValue (dwTlsIndex, (void *) value))
+    return EINVAL;
+
   return 0;
 }
 
 void *
 pthread_key::get ()
 {
-  set_errno (0);
-  return TlsGetValue (dwTlsIndex);
+  void *result;
+  int last_error = GetLastError ();
+
+  if (dwTlsIndex == TLS_OUT_OF_INDEXES)
+    result = NULL;
+  else
+    result = TlsGetValue (dwTlsIndex);
+
+  SetLastError (last_error);
+
+  return result;
 }
 
 void
@@ -1884,8 +1895,8 @@ __pthread_setspecific (pthread_key_t key
 {
   if (verifyable_object_isvalid (&key, PTHREAD_KEY_MAGIC) != VALID_OBJECT)
     return EINVAL;
-  (key)->set (value);
-  return 0;
+
+  return (key)->set (value);
 }
 
 void *
@@ -1895,7 +1906,6 @@ __pthread_getspecific (pthread_key_t key
     return NULL;
 
   return (key)->get ();
-
 }
 
 /*Thread synchronisation */