Index: src/main/java/org/jbpm/pvm/internal/query/TaskQueryImpl.java
===================================================================
--- src/main/java/org/jbpm/pvm/internal/query/TaskQueryImpl.java	(revision 6289)
+++ src/main/java/org/jbpm/pvm/internal/query/TaskQueryImpl.java	(working copy)
@@ -132,6 +132,15 @@
         query.setParameterList("candidateGroupIds", groupIds);
       }
     }
+    if(processDefinitionId != null){
+        query.setString("processDefinitionId", processDefinitionId);
+    }
+    if(processInstanceId != null){
+        query.setString("processInstanceId", processInstanceId);
+    }
+    if(activityName != null){
+        query.setString("activityName", activityName);
+    }
   }
 
   public String hql() {
@@ -181,15 +190,15 @@
     }
     
     if (processInstanceId!=null) {
-      appendWhereClause("task.processInstance.id = '"+processInstanceId+"' ", hql);
+      appendWhereClause("task.processInstance.id = :processInstanceId ", hql);
     }
 
     if (activityName!=null) {
-      appendWhereClause("task.execution.activityName = '"+activityName+"' ", hql);
+      appendWhereClause("task.execution.activityName = :activityName ", hql);
     }
 
     if (processDefinitionId!=null) {
-      appendWhereClause("task.processInstance.processDefinitionId = '"+processDefinitionId+"' ", hql);
+      appendWhereClause("task.processInstance.processDefinitionId = :processDefinitionId ", hql);
     }
 
     if (assignee!=null) {