diff --git a/src/Mod/Sketcher/App/SketchObject.cpp b/src/Mod/Sketcher/App/SketchObject.cpp
index d4c240c34..fa3964b9b 100644
--- a/src/Mod/Sketcher/App/SketchObject.cpp
+++ b/src/Mod/Sketcher/App/SketchObject.cpp
@@ -1702,13 +1702,26 @@ int SketchObject::trim(int GeoId, const Base::Vector3d& point)
     return -1;
 }
 
-bool SketchObject::isExternalAllowed(App::Document *pDoc, App::DocumentObject *pObj) const
+bool SketchObject::isExternalAllowed(App::Document *pDoc, App::DocumentObject *pObj, eReasonList* rsn) const
 {
+    if (rsn)
+        *rsn = rlAllowed;
+
     // Externals outside of the Document are NOT allowed
-    if (this->getDocument() != pDoc)
+    if (this->getDocument() != pDoc){
+        if (rsn)
+            *rsn = rlOtherDoc;
         return false;    
+    }
+
+    //circular reference prevention
     try {
-        return this->testIfLinkDAGCompatible(pObj);
+        if (!(this->testIfLinkDAGCompatible(pObj))){
+            if (rsn)
+                *rsn = rlCircularReference;
+            return false
+            ;
+        }
     } catch (Base::Exception &e) {
         Base::Console().Warning("Probably, there is a circular reference in the document. Error: %s\n", e.what());
         return true; //prohibiting this reference won't remove the problem anyway...
@@ -1721,6 +1734,8 @@ bool SketchObject::isExternalAllowed(App::Document *pDoc, App::DocumentObject *p
     if (body != NULL) {
         if ( ! body->hasFeature (pObj) && !this->allowOtherBody ) {
             // Selection outside of body not allowed if flag is not set
+            if (rsn)
+                *rsn = rlOtherPart;
             return false;
         }
     } else {
diff --git a/src/Mod/Sketcher/App/SketchObject.h b/src/Mod/Sketcher/App/SketchObject.h
index 15c38670c..39afacf7c 100644
--- a/src/Mod/Sketcher/App/SketchObject.h
+++ b/src/Mod/Sketcher/App/SketchObject.h
@@ -261,8 +261,16 @@ public:
 
     /// Flag to allow external geometry from other bodies than the one this sketch belongs to
     bool allowOtherBody;
-    /// Return true if this object is allowed as external geometry for the sketch
-    bool isExternalAllowed(App::Document *pDoc, App::DocumentObject *pObj) const;
+
+    enum eReasonList{
+        rlAllowed,
+        rlOtherDoc,
+        rlCircularReference,
+        rlOtherPart,
+    };
+    /// Return true if this object is allowed as external geometry for the
+    /// sketch. rsn argument recieves the reason for disallowing.
+    bool isExternalAllowed(App::Document *pDoc, App::DocumentObject *pObj, eReasonList* rsn = 0) const;
 
 protected:
     /// get called by the container when a property has changed
diff --git a/src/Mod/Sketcher/Gui/CommandCreateGeo.cpp b/src/Mod/Sketcher/Gui/CommandCreateGeo.cpp
index 95544db0e..3d1a79dd4 100644
--- a/src/Mod/Sketcher/Gui/CommandCreateGeo.cpp
+++ b/src/Mod/Sketcher/Gui/CommandCreateGeo.cpp
@@ -4475,8 +4475,21 @@ namespace SketcherGui {
         bool allow(App::Document *pDoc, App::DocumentObject *pObj, const char *sSubName)
         {
             Sketcher::SketchObject *sketch = static_cast<Sketcher::SketchObject*>(object);
-            if (!sketch->isExternalAllowed(pDoc, pObj))
+            Sketcher::SketchObject::eReasonList msg;
+            if (!sketch->isExternalAllowed(pDoc, pObj, &msg)){
+                switch(msg){
+                case Sketcher::SketchObject::rlCircularReference:
+                    this->notAllowedReason = QT_TR_NOOP("Linking this will cause circular dependency.");
+                break;
+                case Sketcher::SketchObject::rlOtherDoc:
+                    this->notAllowedReason = QT_TR_NOOP("This object is in another document.");
+                break;
+                case Sketcher::SketchObject::rlOtherPart:
+                    this->notAllowedReason = QT_TR_NOOP("This object belongs to another part, can't link.");
+                break;
+                }
                 return false;
+            }
 
             // Note: its better to search the support of the sketch in case the sketch support is a base plane
             //Part::BodyBase* body = Part::BodyBase::findBodyOf(sketch);