diff --git a/ChangeLog b/ChangeLog
index 76be75a85..f81527da9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2010-11-26  Johnson Y. Yan  <yinsen_yan@foxitsoftware.com>
+
+	[truetype] Better multi-threading support.
+
+	* src/truetype/ttinterp.c (TT_Load_Context): Reset glyph zone
+	references.
+
 2010-11-23  John Tytgat  <John.Tytgat@esko.com>
 
 	* src/psaux/t1decode.c (t1_decoder_parse_charstring): Expand
diff --git a/src/truetype/ttinterp.c b/src/truetype/ttinterp.c
index 34cd25879..f55b8eeab 100644
--- a/src/truetype/ttinterp.c
+++ b/src/truetype/ttinterp.c
@@ -595,6 +595,12 @@
       exec->storage   = size->storage;
 
       exec->twilight  = size->twilight;
+
+      /* In case of multi-threading it can happen that the old size object */
+      /* no longer exists, thus we must clear all glyph zone references.   */
+      ft_memset( &exec->zp0, 0, sizeof ( exec->zp0 ) );
+      exec->zp1 = exec->zp0;
+      exec->zp2 = exec->zp0;
     }
 
     /* XXX: We reserve a little more elements on the stack to deal safely */