diff --git a/src/Mod/Sketcher/App/ConstraintPyImp.cpp b/src/Mod/Sketcher/App/ConstraintPyImp.cpp
index 8702de990b..99c85f96d8 100644
--- a/src/Mod/Sketcher/App/ConstraintPyImp.cpp
+++ b/src/Mod/Sketcher/App/ConstraintPyImp.cpp
@@ -158,6 +158,13 @@ int ConstraintPy::PyInit(PyObject* args, PyObject* /*kwd*/)
                 this->getConstraintPtr()->LabelPosition = 10;
                 valid = true;
             }
+            else if (strcmp("Diameter",ConstraintType) == 0) {
+                this->getConstraintPtr()->Type = Diameter;
+                // set a value that is out of range of result of atan2
+                // this value is handled in ViewProviderSketch
+                this->getConstraintPtr()->LabelPosition = 10;
+                valid = true;
+            }
             if (valid) {
                 this->getConstraintPtr()->First    = FirstIndex;
                 this->getConstraintPtr()->setValue(Value);
@@ -491,6 +498,7 @@ std::string ConstraintPy::representation(void) const
         case Vertical           : result << "'Vertical' (" << getConstraintPtr()->First << ")>";break;
         case Block            	: result << "'Block' (" << getConstraintPtr()->First << ")>";break;
         case Radius             : result << "'Radius'>";break;
+        case Diameter           : result << "'Diameter'>";break;
         case Parallel           : result << "'Parallel'>";break;
         case Tangent            :
             if (this->getConstraintPtr()->Third == Constraint::GeoUndef)
@@ -541,6 +549,7 @@ Py::String ConstraintPy::getType(void) const
         case Vertical           : return Py::String("Vertical");break;
         case Block              : return Py::String("Block");break;
         case Radius             : return Py::String("Radius");break;
+        case Diameter           : return Py::String("Diameter");break;
         case Parallel           : return Py::String("Parallel");break;
         case Tangent            : return Py::String("Tangent");break;
         case Perpendicular      : return Py::String("Perpendicular");break;