diff --git a/src/Mod/Sketcher/App/SketchObject.cpp b/src/Mod/Sketcher/App/SketchObject.cpp
index ba5719770b..3941a9cd20 100644
--- a/src/Mod/Sketcher/App/SketchObject.cpp
+++ b/src/Mod/Sketcher/App/SketchObject.cpp
@@ -247,16 +247,22 @@ int SketchObject::delGeometry(int GeoNbr)
     for (std::vector<Constraint *>::const_iterator it = constraints.begin();
          it != constraints.end(); ++it) {
         if ((*it)->First != GeoNbr && (*it)->Second != GeoNbr) {
-            if ((*it)->First > GeoNbr)
-                (*it)->First -= 1;
-            if ((*it)->Second > GeoNbr)
-                (*it)->Second -= 1;
-            newConstraints.push_back(*it);
+            Constraint *copiedConstr = (*it)->clone();
+            if (copiedConstr->First > GeoNbr)
+                copiedConstr->First -= 1;
+            if (copiedConstr->Second > GeoNbr)
+                copiedConstr->Second -= 1;
+            newConstraints.push_back(copiedConstr);
         }
     }
 
-    this->Constraints.setValues(newConstraints);
+    // temporarily empty constraints list in order to avoid invalid constraints
+    // during manipulation of the geometry list
+    std::vector< Constraint * > emptyConstraints(0);
+    this->Constraints.setValues(emptyConstraints);
+
     this->Geometry.setValues(newVals);
+    this->Constraints.setValues(newConstraints);
     rebuildVertexIndex();
     return 0;
 }
diff --git a/src/Mod/Sketcher/Gui/ViewProviderSketch.cpp b/src/Mod/Sketcher/Gui/ViewProviderSketch.cpp
index 25c50e4e79..853dab5d35 100644
--- a/src/Mod/Sketcher/Gui/ViewProviderSketch.cpp
+++ b/src/Mod/Sketcher/Gui/ViewProviderSketch.cpp
@@ -1483,6 +1483,7 @@ float ViewProviderSketch::getScaleFactor()
         return 1.f;
     }
 }
+
 void ViewProviderSketch::draw(bool temp)
 {
     assert(edit);
@@ -1669,7 +1670,7 @@ Restart:
                     // get the geometry
                     const Part::Geometry *geo = (*geomlist)[Constr->First];
                     // Vertical can only be a GeomLineSegment
-                    assert(geo->getTypeId()== Part::GeomLineSegment::getClassTypeId());
+                    assert(geo->getTypeId() == Part::GeomLineSegment::getClassTypeId());
                     const Part::GeomLineSegment *lineSeg = dynamic_cast<const Part::GeomLineSegment *>(geo);
 
                     // calculate the half distance between the start and endpoint
@@ -2938,7 +2939,6 @@ Sketcher::SketchObject *ViewProviderSketch::getSketchObject(void) const
     return dynamic_cast<Sketcher::SketchObject *>(pcObject);
 }
 
-
 bool ViewProviderSketch::onDelete(const std::vector<std::string> &subList)
 {
     //FIXME use the selection subelements instead of the Sel Sets...