diff --git a/src/Mod/Part/App/BSplineCurvePyImp.cpp b/src/Mod/Part/App/BSplineCurvePyImp.cpp
index d3b02b6c08..f07ce26f1d 100644
--- a/src/Mod/Part/App/BSplineCurvePyImp.cpp
+++ b/src/Mod/Part/App/BSplineCurvePyImp.cpp
@@ -1241,7 +1241,15 @@ PyObject* BSplineCurvePy::buildFromPolesMultsKnots(PyObject *args, PyObject *key
                 occmults.SetValue(occmults.Length(), degree+1);
                 sum_of_mults = occmults.Length()+2*degree;
             }
-            else { sum_of_mults = occmults.Length()-1;}
+            else {
+                sum_of_mults = occmults.Length()-1;
+            }
+        }
+        // check multiplicity of inner knots
+        for (Standard_Integer i=2; i < occmults.Length(); i++) {
+            if (occmults(i) > degree) {
+                Standard_Failure::Raise("multiplicity of inner knot higher than degree");
+            }
         }
         if (knots != Py_None) { //knots are given
             Py::Sequence knotssq(knots);
diff --git a/src/Mod/Part/App/BSplineSurfacePyImp.cpp b/src/Mod/Part/App/BSplineSurfacePyImp.cpp
index 44a96456c1..33ae6d96a7 100644
--- a/src/Mod/Part/App/BSplineSurfacePyImp.cpp
+++ b/src/Mod/Part/App/BSplineSurfacePyImp.cpp
@@ -1514,6 +1514,18 @@ PyObject* BSplineSurfacePy::buildFromPolesMultsKnots(PyObject *args, PyObject *k
             (PyObject_Not(vperiodic) && sum_of_vmults - vdegree -1 != lv)) {
             Standard_Failure::Raise("number of poles and sum of mults mismatch");
         }
+        // check multiplicity of inner knots
+        for (Standard_Integer i=2; i < occumults.Length(); i++) {
+            if (occumults(i) > udegree) {
+                Standard_Failure::Raise("multiplicity of inner knot higher than degree");
+            }
+        }
+        for (Standard_Integer i=2; i < occvmults.Length(); i++) {
+            if (occvmults(i) > vdegree) {
+                Standard_Failure::Raise("multiplicity of inner knot higher than degree");
+            }
+        }
+
         Handle(Geom_BSplineSurface) spline = new Geom_BSplineSurface(occpoles,occweights,
             occuknots,occvknots,occumults,occvmults,udegree,vdegree,
             PyObject_IsTrue(uperiodic) ? Standard_True : Standard_False,