diff --git a/src/Mod/Mesh/App/Core/MeshIO.cpp b/src/Mod/Mesh/App/Core/MeshIO.cpp
index 75f12c4af..d054ae261 100644
--- a/src/Mod/Mesh/App/Core/MeshIO.cpp
+++ b/src/Mod/Mesh/App/Core/MeshIO.cpp
@@ -312,7 +312,7 @@ bool MeshInput::LoadOBJ (std::istream &rstrIn)
         bool ok = true;
         for (int i=0;i<3;i++) {
             if (it->_aulPoints[i] >= ct) {
-                Base::Console().Warning("Face index %ld out of range\n", it->_aulPoints[i]);
+                Base::Console().Warning("Face index %lu out of range\n", it->_aulPoints[i]);
                 ok = false;
             }
         }
@@ -435,7 +435,7 @@ bool MeshInput::LoadOFF (std::istream &rstrIn)
         bool ok = true;
         for (int i=0;i<3;i++) {
             if (it->_aulPoints[i] >= ct) {
-                Base::Console().Warning("Face index %ld out of range\n", it->_aulPoints[i]);
+                Base::Console().Warning("Face index %lu out of range\n", it->_aulPoints[i]);
                 ok = false;
             }
         }
diff --git a/src/Mod/Mesh/App/Core/MeshKernel.cpp b/src/Mod/Mesh/App/Core/MeshKernel.cpp
index fb4ce96b3..fc53e1f23 100644
--- a/src/Mod/Mesh/App/Core/MeshKernel.cpp
+++ b/src/Mod/Mesh/App/Core/MeshKernel.cpp
@@ -809,6 +809,7 @@ void MeshKernel::Read (std::istream &rclIn)
     str >> magic >> version;
     swap_magic = magic; Base::SwapEndian(swap_magic);
     swap_version = version; Base::SwapEndian(swap_version);
+    uint32_t open_edge = 0xffffffff; // value to mark an open edge
 
     // is it the new or old format?
     bool new_format = false;
@@ -846,10 +847,25 @@ void MeshKernel::Read (std::istream &rclIn)
                 it->_aulPoints[1] = v2;
                 it->_aulPoints[2] = v3;
 
+                // On systems where an 'unsigned long' is a 64-bit value
+                // the empty neighbour must be explicitly set to 'ULONG_MAX'
+                // because in algorithms this value is always used to check
+                // for open edges.
                 str >> v1 >> v2 >> v3;
-                it->_aulNeighbours[0] = v1;
-                it->_aulNeighbours[1] = v2;
-                it->_aulNeighbours[2] = v3;
+                if (v1 < open_edge)
+                    it->_aulNeighbours[0] = v1;
+                else
+                    it->_aulNeighbours[0] = ULONG_MAX;
+
+                if (v2 < open_edge)
+                    it->_aulNeighbours[1] = v2;
+                else
+                    it->_aulNeighbours[1] = ULONG_MAX;
+
+                if (v3 < open_edge)
+                    it->_aulNeighbours[2] = v3;
+                else
+                    it->_aulNeighbours[2] = ULONG_MAX;
             }
 
             str >> _clBoundBox.MinX >> _clBoundBox.MaxX;
diff --git a/src/Mod/Mesh/Gui/ViewProvider.cpp b/src/Mod/Mesh/Gui/ViewProvider.cpp
index 18d220af3..f1d372508 100644
--- a/src/Mod/Mesh/Gui/ViewProvider.cpp
+++ b/src/Mod/Mesh/Gui/ViewProvider.cpp
@@ -1385,7 +1385,7 @@ void ViewProviderMesh::faceInfo(unsigned long uFacet)
     if (uFacet < facets.size()) {
         MeshCore::MeshFacet face = facets[uFacet];
         MeshCore::MeshGeomFacet tria = rKernel.GetFacet(face);
-        Base::Console().Message("Mesh: %s Facet %ld: Points: <%ld, %ld, %ld>, Neighbours: <%ld, %ld, %ld>\n"
+        Base::Console().Message("Mesh: %s Facet %lu: Points: <%lu, %lu, %lu>, Neighbours: <%lu, %lu, %lu>\n"
             "Triangle: <[%.6f, %.6f, %.6f], [%.6f, %.6f, %.6f], [%.6f, %.6f, %.6f]>\n", fea->getNameInDocument(), uFacet, 
             face._aulPoints[0], face._aulPoints[1], face._aulPoints[2], 
             face._aulNeighbours[0], face._aulNeighbours[1], face._aulNeighbours[2],
diff --git a/src/Mod/MeshPart/App/CurveProjector.cpp b/src/Mod/MeshPart/App/CurveProjector.cpp
index 38fb3ba20..3e9f3e4b9 100644
--- a/src/Mod/MeshPart/App/CurveProjector.cpp
+++ b/src/Mod/MeshPart/App/CurveProjector.cpp
@@ -184,7 +184,7 @@ void CurveProjectorShape::projectCurve( const TopoDS_Edge& aEdge,
         // more the one intersection (@ToDo)
         }else if(Alg.NbPoints() > 1){
           PointOnEdge[i] = Base::Vector3f(FLOAT_MAX,0,0);
-          Base::Console().Log("MeshAlgos::projectCurve(): More then one intersection in Facet %ld, Edge %d\n",uCurFacetIdx,i);
+          Base::Console().Log("MeshAlgos::projectCurve(): More then one intersection in Facet %lu, Edge %d\n",uCurFacetIdx,i);
         }
       }
     }
@@ -202,7 +202,7 @@ void CurveProjectorShape::projectCurve( const TopoDS_Edge& aEdge,
       cResultPoint = cSplitPoint;
       GoOn = true;
     }else{
-      Base::Console().Log("MeshAlgos::projectCurve(): Posibel reentry in Facet %ld\n", uCurFacetIdx);
+      Base::Console().Log("MeshAlgos::projectCurve(): Possible reentry in Facet %lu\n", uCurFacetIdx);
     }
 
     if( uCurFacetIdx == uStartFacetIdx )
diff --git a/src/Mod/ReverseEngineering/Gui/Command.cpp b/src/Mod/ReverseEngineering/Gui/Command.cpp
index 7c5a0813d..1df871e11 100644
--- a/src/Mod/ReverseEngineering/Gui/Command.cpp
+++ b/src/Mod/ReverseEngineering/Gui/Command.cpp
@@ -170,7 +170,7 @@ void CmdApproxPlane::activated(int iMsg)
                 double q0, q1, q2, q3;
                 pm.getRotation().getValue(q0, q1, q2, q3);
 
-                Base::Console().Log("RMS value for plane fit with %ld points: %.4f\n", aData.size(), sigma);
+                Base::Console().Log("RMS value for plane fit with %lu points: %.4f\n", aData.size(), sigma);
                 Base::Console().Log("  Plane base(%.4f, %.4f, %.4f)\n", base.x, base.y, base.z);
                 Base::Console().Log("  Plane normal(%.4f, %.4f, %.4f)\n", norm.x, norm.y, norm.z);