diff --git a/src/App/ApplicationPy.cpp b/src/App/ApplicationPy.cpp
index 2336398bfb..345cce3895 100644
--- a/src/App/ApplicationPy.cpp
+++ b/src/App/ApplicationPy.cpp
@@ -893,7 +893,7 @@ PyObject *Application::sGetDependentObjects(PyObject * /*self*/, PyObject *args)
     std::vector<App::DocumentObject*> objs;
     if(PySequence_Check(obj)) {
         Py::Sequence seq(obj);
-        for(size_t i=0;i<seq.size();++i) {
+        for(Py_ssize_t i=0;i<seq.size();++i) {
             if(!PyObject_TypeCheck(seq[i].ptr(),&DocumentObjectPy::Type)) {
                 PyErr_SetString(PyExc_TypeError, "Expect element in sequence to be of type document object");
                 return 0;
diff --git a/src/App/DocumentPyImp.cpp b/src/App/DocumentPyImp.cpp
index 9587aada7a..fc5fba2526 100644
--- a/src/App/DocumentPyImp.cpp
+++ b/src/App/DocumentPyImp.cpp
@@ -300,7 +300,7 @@ PyObject*  DocumentPy::copyObject(PyObject *args)
     bool single = false;
     if (PySequence_Check(obj)) {
         Py::Sequence seq(obj);
-        for (size_t i=0;i<seq.size();++i) {
+        for (Py_ssize_t i=0;i<seq.size();++i) {
             if (!PyObject_TypeCheck(seq[i].ptr(),&DocumentObjectPy::Type)) {
                 PyErr_SetString(PyExc_TypeError, "Expect element in sequence to be of type document object");
                 return 0;
@@ -339,7 +339,7 @@ PyObject*  DocumentPy::importLinks(PyObject *args)
     std::vector<App::DocumentObject*> objs;
     if (PySequence_Check(obj)) {
         Py::Sequence seq(obj);
-        for (size_t i=0;i<seq.size();++i) {
+        for (Py_ssize_t i=0;i<seq.size();++i) {
             if (!PyObject_TypeCheck(seq[i].ptr(),&DocumentObjectPy::Type)) {
                 PyErr_SetString(PyExc_TypeError, "Expect element in sequence to be of type document object");
                 return 0;
@@ -487,7 +487,7 @@ PyObject*  DocumentPy::recompute(PyObject * args)
             }
 
             Py::Sequence seq(pyobjs);
-            for (size_t i=0;i<seq.size();++i) {
+            for (Py_ssize_t i=0;i<seq.size();++i) {
                 if (!PyObject_TypeCheck(seq[i].ptr(), &DocumentObjectPy::Type)) {
                     PyErr_SetString(PyExc_TypeError, "Expect element in sequence to be of type document object");
                     return nullptr;
diff --git a/src/App/FeaturePython.cpp b/src/App/FeaturePython.cpp
index 4d6126c232..5739c9fbaa 100644
--- a/src/App/FeaturePython.cpp
+++ b/src/App/FeaturePython.cpp
@@ -296,7 +296,7 @@ bool FeaturePythonImp::getSubObjects(std::vector<std::string> &ret, int reason)
         if(!res.isSequence())
             throw Py::TypeError("getSubObjects expects return type of tuple");
         Py::Sequence seq(res);
-        for(size_t i=0;i<seq.length();++i) {
+        for(Py_ssize_t i=0;i<seq.length();++i) {
             Py::Object name(seq[i].ptr());
             if(!name.isString())
                 throw Py::TypeError("getSubObjects expects string in returned sequence");
diff --git a/src/App/LinkBaseExtensionPyImp.cpp b/src/App/LinkBaseExtensionPyImp.cpp
index 014404b89e..be38bc2fc5 100644
--- a/src/App/LinkBaseExtensionPyImp.cpp
+++ b/src/App/LinkBaseExtensionPyImp.cpp
@@ -258,7 +258,7 @@ PyObject* LinkBaseExtensionPy::setLink(PyObject *_args)
         }else if(PySequence_Check(pcObj)) {
             ext->setLink(-1,0);
             Py::Sequence seq(pcObj);
-            for(size_t i=0;i<seq.size();++i)
+            for(Py_ssize_t i=0;i<seq.size();++i)
                 parseLink(ext,i,seq[i].ptr());
         }else
             parseLink(ext,-1,_args);
diff --git a/src/App/PropertyLinks.cpp b/src/App/PropertyLinks.cpp
index 6f47ffbe27..e5435eb422 100644
--- a/src/App/PropertyLinks.cpp
+++ b/src/App/PropertyLinks.cpp
@@ -3546,7 +3546,7 @@ void PropertyXLink::setPyObject(PyObject *value) {
         } else if (pySub.isSequence()) {
             Py::Sequence seq(pySub);
             subs.reserve(seq.size());
-            for(size_t i=0;i<seq.size();++i) {
+            for(Py_ssize_t i=0;i<seq.size();++i) {
                 Py::Object sub(seq[i]);
                 if(!sub.isString())
                     throw Base::TypeError("Expect only string inside second argument");
diff --git a/src/Gui/LinkViewPyImp.cpp b/src/Gui/LinkViewPyImp.cpp
index 7f9ab1f208..53cb2777c2 100644
--- a/src/Gui/LinkViewPyImp.cpp
+++ b/src/Gui/LinkViewPyImp.cpp
@@ -106,7 +106,7 @@ PyObject* LinkViewPy::setMaterial(PyObject *args) {
             Py::Sequence seq(pyObj);
             std::vector<App::Material*> materials;
             materials.resize(seq.size(),0);
-            for(size_t i=0;i<seq.size();++i) {
+            for(Py_ssize_t i=0;i<seq.size();++i) {
                 PyObject* item = seq[i].ptr();
                 if(item == Py_None) continue;
                 if(!PyObject_TypeCheck(item,&App::MaterialPy::Type)) {
@@ -156,7 +156,7 @@ PyObject* LinkViewPy::setTransform(PyObject *args) {
             Py::Sequence seq(pyObj);
             std::vector<Base::Matrix4D*> mat;
             mat.resize(seq.size(),0);
-            for(size_t i=0;i<seq.size();++i) {
+            for(Py_ssize_t i=0;i<seq.size();++i) {
                 PyObject* item = seq[i].ptr();
                 if(!PyObject_TypeCheck(item,&Base::MatrixPy::Type)) {
                     PyErr_SetString(PyExc_TypeError, "exepcting a type of Matrix");
diff --git a/src/Gui/propertyeditor/PropertyItem.cpp b/src/Gui/propertyeditor/PropertyItem.cpp
index 2fb5be2061..f59c1ad04a 100644
--- a/src/Gui/propertyeditor/PropertyItem.cpp
+++ b/src/Gui/propertyeditor/PropertyItem.cpp
@@ -357,7 +357,7 @@ QVariant PropertyItem::toString(const QVariant& prop) const
         ss << '[';
         Py::Sequence seq(pyobj);
         bool first = true;
-        size_t i=0;
+        Py_ssize_t i=0;
         for (i=0; i<2 && i < seq.size(); ++i) {
             if (first)
                 first = false;