diff --git a/libjava/ChangeLog b/libjava/ChangeLog
index 9d608040918..5092814932a 100644
--- a/libjava/ChangeLog
+++ b/libjava/ChangeLog
@@ -1,5 +1,9 @@
 1999-09-08  Tom Tromey  <tromey@cygnus.com>
 
+	* include/posix-threads.h (_Jv_PthreadCheckMonitor): Reverted
+	previous change and implemented a correct test in the __m_count
+	case.
+
 	* include/posix-threads.h (_Jv_PthreadCheckMonitor): Changed test
 	in __m_count case.
 
diff --git a/libjava/include/posix-threads.h b/libjava/include/posix-threads.h
index 00a918fab27..38629f44b01 100644
--- a/libjava/include/posix-threads.h
+++ b/libjava/include/posix-threads.h
@@ -114,7 +114,9 @@ _Jv_PthreadCheckMonitor (_Jv_Mutex_t *mu)
   // On Linux we exploit knowledge of the implementation.
   int r = pmu->m_count == 1;
 #elif defined (PTHREAD_MUTEX_HAVE___M_COUNT)
-  int r = (pthread_t) pmu->__m_owner == pthread_self ();
+  // In glibc 2.1, the first time the mutex is grabbed __m_count is
+  // set to 0 and __m_owner is set to pthread_self().
+  int r = ! pmu->__m_count;
 #else
   int r = mu->count == 0;
 #endif