diff --git a/rtt/base/OperationCallerInterface.cpp b/rtt/base/OperationCallerInterface.cpp
index 8094dd5ad..4d689d5d6 100644
--- a/rtt/base/OperationCallerInterface.cpp
+++ b/rtt/base/OperationCallerInterface.cpp
@@ -31,6 +31,14 @@ bool OperationCallerInterface::setThread(ExecutionThread et, ExecutionEngine* ex
     return true;
 }
 
+bool OperationCallerInterface::isSend()
+{
+    if ( met == ClientThread ) return false;
+    // OwnThread case:
+    if ( myengine->getActivity()->thread()->isSelf() ) return false;
+    return true; // all other OwnThread cases
+}
+
 ExecutionEngine* OperationCallerInterface::getMessageProcessor() const 
 { 
     ExecutionEngine* ret = (met == OwnThread ? myengine : GlobalEngine::Instance()); 
diff --git a/rtt/base/OperationCallerInterface.hpp b/rtt/base/OperationCallerInterface.hpp
index 2252fd5db..e3176d878 100644
--- a/rtt/base/OperationCallerInterface.hpp
+++ b/rtt/base/OperationCallerInterface.hpp
@@ -75,8 +75,10 @@ namespace RTT
 
             /**
              * Helpful function to tell us if this operations is to be sent or not.
+	     * Sending is only required if the operation is OwnThread *and* in a
+	     * different thread than the caller.
              */
-            bool isSend() { return met == OwnThread && myengine != caller; }
+            bool isSend();
 
             ExecutionEngine* getMessageProcessor() const;
 
diff --git a/rtt/internal/LocalOperationCaller.hpp b/rtt/internal/LocalOperationCaller.hpp
index 33bdd6bb0..4f309b5cf 100644
--- a/rtt/internal/LocalOperationCaller.hpp
+++ b/rtt/internal/LocalOperationCaller.hpp
@@ -285,6 +285,7 @@ namespace RTT
                 if (!this->caller) {
                     log(Error) << "You're using call() an OwnThread operation or collect() on a sent operation without setting a caller in the OperationCaller. This often causes deadlocks." <<endlog();
                     log(Error) << "Use this->engine() in a component or GlobalEngine::Instance() in a non-component function. Returning a CollectFailure." <<endlog();
+                    assert( false && "You forgot to use setCaller(). See Orocos LOG messages for explanation.");
                     return false;
                 }
                 return true;