diff --git a/lib/sqlite/sqlite3.c b/lib/sqlite/sqlite3.c
index e60c4579b..d04fa3801 100644
--- a/lib/sqlite/sqlite3.c
+++ b/lib/sqlite/sqlite3.c
@@ -431,8 +431,12 @@
 ** See also ticket #2741.
 */
 #if !defined(_XOPEN_SOURCE) && !defined(__DARWIN__) && !defined(__APPLE__) && SQLITE_THREADSAFE
+#ifdef __sun
+#  define _XOPEN_SOURCE 600
+#else
 #  define _XOPEN_SOURCE 500  /* Needed to enable pthread recursive mutexes */
 #endif
+#endif
 
 /*
 ** The TCL headers are only needed when compiling the TCL bindings.