diff --git a/src/Mod/Sketcher/App/SketchObject.cpp b/src/Mod/Sketcher/App/SketchObject.cpp
index 9b9506650244..b2abe8ec8ac5 100644
--- a/src/Mod/Sketcher/App/SketchObject.cpp
+++ b/src/Mod/Sketcher/App/SketchObject.cpp
@@ -2160,6 +2160,47 @@ void SketchObject::appendRedundantMsg(const std::vector<int> &redundant, std::st
     msg = ss.str();
 }
 
+bool SketchObject::evaluateConstraint(const Constraint *constraint) const
+{
+    int intGeoCount = getHighestCurveIndex() + 1;
+    int extGeoCount = getExternalGeometryCount();
+
+    switch (constraint->Type) {
+        case Horizontal:
+        case Vertical:
+        case Radius:
+        case Distance:
+        case DistanceX:
+        case DistanceY:
+            if (constraint->First < -extGeoCount || constraint->First >= intGeoCount)
+                return false;
+            break;
+        case Coincident:
+        case Perpendicular:
+        case Parallel:
+        case Equal:
+        case PointOnObject:
+        case Tangent:
+        case Symmetric:
+            if (constraint->First < -extGeoCount || constraint->First >= intGeoCount)
+                return false;
+            if (constraint->Second < -extGeoCount || constraint->Second >= intGeoCount)
+                return false;
+            break;
+        case Angle:
+            if (constraint->First < -extGeoCount || constraint->First >= intGeoCount)
+                return false;
+            if ((constraint->Second < -extGeoCount || constraint->Second >= intGeoCount) &&
+                 constraint->Second != Constraint::GeoUndef)
+                 return false;
+            break;
+        default:
+            break;
+    }
+
+    return true;
+}
+
 bool SketchObject::evaluateConstraints() const
 {
     int intGeoCount = getHighestCurveIndex() + 1;
@@ -2174,37 +2215,8 @@ bool SketchObject::evaluateConstraints() const
 
     std::vector<Sketcher::Constraint *>::const_iterator it;
     for (it = constraints.begin(); it != constraints.end(); ++it) {
-        switch ((*it)->Type) {
-            case Horizontal:
-            case Vertical:
-            case Radius:
-            case Distance:
-            case DistanceX:
-            case DistanceY:
-                if ((*it)->First < -extGeoCount || (*it)->First >= intGeoCount)
-                    return false;
-                break;
-            case Perpendicular:
-            case Parallel:
-            case Equal:
-            case PointOnObject:
-            case Tangent:
-            case Symmetric:
-                if ((*it)->First < -extGeoCount || (*it)->First >= intGeoCount)
-                    return false;
-                if ((*it)->Second < -extGeoCount || (*it)->Second >= intGeoCount)
-                    return false;
-                break;
-            case Angle:
-                if ((*it)->First < -extGeoCount || (*it)->First >= intGeoCount)
-                    return false;
-                if (((*it)->Second < -extGeoCount || (*it)->Second >= intGeoCount) &&
-                     (*it)->Second != Constraint::GeoUndef)
-                     return false;
-                break;
-            default:
-                break;
-        }
+        if (!evaluateConstraint(*it))
+            return false;
     }
 
     return true;
diff --git a/src/Mod/Sketcher/App/SketchObject.h b/src/Mod/Sketcher/App/SketchObject.h
index 586e0d197b72..38fac9ce5fb4 100644
--- a/src/Mod/Sketcher/App/SketchObject.h
+++ b/src/Mod/Sketcher/App/SketchObject.h
@@ -164,6 +164,8 @@ class SketcherExport SketchObject : public Part::Part2DObject
     virtual Base::Axis getAxis(int axId) const;
     /// verify and accept the assigned geometry
     virtual void acceptGeometry();
+    /// Check if constraint has invalid indexes
+    bool evaluateConstraint(const Constraint *constraint) const;
     /// Check for constraints with invalid indexes
     bool evaluateConstraints() const;
     /// Remove constraints with invalid indexes
diff --git a/src/Mod/Sketcher/App/SketchObjectPyImp.cpp b/src/Mod/Sketcher/App/SketchObjectPyImp.cpp
index fabea7da2e0e..c1e07e255f47 100644
--- a/src/Mod/Sketcher/App/SketchObjectPyImp.cpp
+++ b/src/Mod/Sketcher/App/SketchObjectPyImp.cpp
@@ -236,6 +236,10 @@ PyObject* SketchObjectPy::addConstraint(PyObject *args)
 
     if (PyObject_TypeCheck(pcObj, &(Sketcher::ConstraintPy::Type))) {
         Sketcher::Constraint *constr = static_cast<Sketcher::ConstraintPy*>(pcObj)->getConstraintPtr();
+        if (!this->getSketchObjectPtr()->evaluateConstraint(constr)) {
+            PyErr_SetString(PyExc_IndexError, "Constraint has invalid indexes");
+            return 0;
+        }
         int ret = this->getSketchObjectPtr()->addConstraint(constr);
         this->getSketchObjectPtr()->solve();
         return Py::new_reference_to(Py::Int(ret));
@@ -251,6 +255,12 @@ PyObject* SketchObjectPy::addConstraint(PyObject *args)
             }
         }
 
+        for (std::vector<Constraint*>::iterator it = values.begin(); it != values.end(); ++it) {
+            if (!this->getSketchObjectPtr()->evaluateConstraint(*it)) {
+                PyErr_SetString(PyExc_IndexError, "Constraint has invalid indexes");
+                return 0;
+            }
+        }
         int ret = getSketchObjectPtr()->addConstraints(values) + 1;
         std::size_t numCon = values.size();
         Py::Tuple tuple(numCon);