diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 9f959c176da..4b1b74e6e8f 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2010-09-22  Joel Brobecker  <brobecker@adacore.com>
+
+	* ada-tasks.c (read_atcb): Do not compute the task ptid when
+	debugging a core file.
+
 2010-09-22  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	Code cleanup.
diff --git a/gdb/ada-tasks.c b/gdb/ada-tasks.c
index f57f44ff96e..8e42252d42e 100644
--- a/gdb/ada-tasks.c
+++ b/gdb/ada-tasks.c
@@ -583,9 +583,18 @@ read_atcb (CORE_ADDR task_id, struct ada_task_info *task_info)
         }
     }
 
-  /* And finally, compute the task ptid.  */
+  /* And finally, compute the task ptid.  Note that there are situations
+     where this cannot be determined:
+       - The task is no longer alive - the ptid is irrelevant;
+       - We are debugging a core file - the thread is not always
+         completely preserved for us to link back a task to its
+         underlying thread.  Since we do not support task switching
+         when debugging core files anyway, we don't need to compute
+         that task ptid.
+     In either case, we don't need that ptid, and it is just good enough
+     to set it to null_ptid.  */
 
-  if (ada_task_is_alive (task_info))
+  if (target_has_execution && ada_task_is_alive (task_info))
     task_info->ptid = ptid_from_atcb_common (common_value);
   else
     task_info->ptid = null_ptid;