diff --git a/src/entry/Maat_api.cpp b/src/entry/Maat_api.cpp
index 3630b16..2ae109d 100644
--- a/src/entry/Maat_api.cpp
+++ b/src/entry/Maat_api.cpp
@@ -247,7 +247,7 @@ int region_compile(_Maat_feather_t*feather, struct Maat_hierarchy_compile_mid* c
 		
 	}
 	scan_ret=Maat_hierarchy_region_compile(compile_mid, is_last_region, (void**)compile_rule_array, MAX_SCANNER_HIT_NUM);
-	
+	//Maat_hierarchy is rwlock protected, it always returns non-NULL compile_rule.
 	if(scan_ret>1)
 	{
 		qsort(compile_rule_array, scan_ret, sizeof(struct Maat_compile_rule*),
diff --git a/src/entry/Maat_hierarchy.cpp b/src/entry/Maat_hierarchy.cpp
index 3bd14b0..23de1b7 100644
--- a/src/entry/Maat_hierarchy.cpp
+++ b/src/entry/Maat_hierarchy.cpp
@@ -1206,7 +1206,7 @@ int Maat_hierarchy_region_compile(struct Maat_hierarchy_compile_mid* mid, int is
 		{
 			mid->not_clause_hitted_flag=1;
 		}
-		else
+		else if(compile_array[i]->user_data)//For compile may be dettached by Maat_hierarchy_compile_dettach_user_data, only return non-NULL userdata.
 		{		
 			if(r_in_c_cnt>0 ||				//compile hitted becasue of new reigon
 				this_scan_region_hits==0)	//or hit a compile that refer a NOT-logic group in previous scan.