diff --git a/sync.c b/sync.c
index 016c636..f8344bd 100644
--- a/sync.c
+++ b/sync.c
@@ -22,5 +22,10 @@
 #include "php_sync.h"
 
+/* PHP_FE_END not define in php < 5.3.7 */
+#ifndef PHP_FE_END
+#define PHP_FE_END {NULL, NULL, NULL}
+#endif
+
 /* {{{ sync_module_entry
  */
 zend_module_entry sync_module_entry = {
diff --git a/config.m4 b/config.m4
index a386835..877bb61 100644
--- a/config.m4
+++ b/config.m4
@@ -23,6 +23,9 @@ if test "$PHP_SYNC" != "no"; then
     AC_MSG_ERROR([sem_open() is not available on this platform])
   ])
 
+  PHP_ADD_LIBRARY(rt,,SYNC_SHARED_LIBADD)
+  PHP_SUBST(SYNC_SHARED_LIBADD)
+
   dnl # Finish defining the basic extension support.
   AC_DEFINE(HAVE_SYNC, 1, [Whether you have synchronization object support])
   PHP_NEW_EXTENSION(sync, sync.c, $ext_shared)
diff --git a/sync.c b/sync.c
index 529133a..40fe075 100644
--- a/sync.c
+++ b/sync.c
@@ -1120,11 +1120,17 @@ int sync_ReaderWriter_readunlock_internal(sync_ReaderWriter_object *obj)
 	if (!sync_WaitForSemaphore(obj->MxSemRSemMutex, INFINITE))  return 0;
 
 	/* Release the semaphore. */
-	Result = sem_post(obj->MxSemRSemaphore);
-
-	/* Update the event state. */
 	sem_getvalue(obj->MxSemRSemaphore, &Val);
-	if (Val == SEM_VALUE_MAX)  sem_post(obj->MxSemRWaitEvent);
+	if (Val == SEM_VALUE_MAX)  {
+		Result = 1;
+		sem_post(obj->MxSemRWaitEvent);
+	} else {
+		Result = sem_post(obj->MxSemRSemaphore);
+
+		/* Update the event state. */
+		sem_getvalue(obj->MxSemRSemaphore, &Val);
+		if (Val == SEM_VALUE_MAX)  sem_post(obj->MxSemRWaitEvent);
+	}
 
 	if (obj->MxReadLocks)  obj->MxReadLocks--;