diff --git a/modules/activiti-engine/src/main/resources/org/activiti/db/upgrade/activiti.mysql.upgradestep.514.to.515.engine.sql b/modules/activiti-engine/src/main/resources/org/activiti/db/upgrade/activiti.mysql.upgradestep.514.to.515.engine.sql
index 60fab854a5819ffb555b3caf111bd9986c0735f5..7f6d00f95e32a44b7d97a9a0c6d05e2c34d1e499 100644
--- a/modules/activiti-engine/src/main/resources/org/activiti/db/upgrade/activiti.mysql.upgradestep.514.to.515.engine.sql
+++ b/modules/activiti-engine/src/main/resources/org/activiti/db/upgrade/activiti.mysql.upgradestep.514.to.515.engine.sql
@@ -1,6 +1,13 @@
 alter table ACT_RU_TASK 
     add CATEGORY_ varchar(255);
     
-alter table ACT_RU_EXECUTION drop index ACT_UNIQ_RU_BUS_KEY;    
+alter table ACT_RU_EXECUTION drop foreign key ACT_FK_EXE_PROCDEF;  	
+
+alter table ACT_RU_EXECUTION drop index ACT_UNIQ_RU_BUS_KEY;  
+
+alter table ACT_RU_EXECUTION
+    add constraint ACT_FK_EXE_PROCDEF 
+    foreign key (PROC_DEF_ID_) 
+    references ACT_RE_PROCDEF (ID_);
 
 update ACT_GE_PROPERTY set VALUE_ = '5.15-SNAPSHOT' where NAME_ = 'schema.version';