diff --git a/src/calibre/utils/podofo/doc.cpp b/src/calibre/utils/podofo/doc.cpp
index d9cef4c423..83aaa40e1f 100644
--- a/src/calibre/utils/podofo/doc.cpp
+++ b/src/calibre/utils/podofo/doc.cpp
@@ -313,6 +313,7 @@ PDFDoc_create_outline(PDFDoc *self, PyObject *args) {
         try {
             page = self->doc->GetPage(pagenum - 1);
         } catch (const PdfError &err) {
+            (void)err;
             PyErr_Format(PyExc_ValueError, "Invalid page number: %u", pagenum - 1); goto error;
         }
         PdfDestination dest(page, left, top, zoom);
@@ -490,6 +491,7 @@ PDFDoc_alter_links(PDFDoc *self, PyObject *args) {
 										try {
 											page = self->doc->GetPage(pagenum - 1);
 										} catch(const PdfError &err) {
+                                            (void)err;
 											PyErr_Format(PyExc_ValueError, "No page number %d in the PDF file", pagenum);
 											return NULL;
 										}
diff --git a/src/calibre/utils/podofo/fonts.cpp b/src/calibre/utils/podofo/fonts.cpp
index dabfafe5c2..0454bcc20b 100644
--- a/src/calibre/utils/podofo/fonts.cpp
+++ b/src/calibre/utils/podofo/fonts.cpp
@@ -58,7 +58,7 @@ replace_font_references_in_resources(PdfDictionary &resources, const std::unorde
                 try {
                     r = ref_map.at(key);
                 } catch (const std::out_of_range &err) { (void)err; continue; }
-                PdfReference new_ref(static_cast<uint32_t>(r & 0xffffffff), r >> 32);
+                PdfReference new_ref(static_cast<pdf_objnum>(r & 0xffffffff), static_cast<pdf_gennum>(r >> 32));
                 new_font.AddKey(k.first.GetName(), new_ref);
                 changed = true;
             }
@@ -325,12 +325,12 @@ merge_fonts(PDFDoc *self, PyObject *args) {
         c++;
         unsigned long num, gen;
         if (!PyArg_ParseTuple(key, "kk", &num, &gen)) return NULL;
-        uint64_t k = ref_as_integer(num, gen);
-        PdfReference ref(num, gen);
+        uint64_t k = ref_as_integer(static_cast<pdf_objnum>(num), static_cast<pdf_gennum>(gen));
+        PdfReference ref(num, static_cast<pdf_gennum>(gen));
         PdfObject *font = objects.GetObject(ref);
         if (font) remove_font(objects, font);
         if (!PyArg_ParseTuple(value, "kk", &num, &gen)) return NULL;
-        uint64_t v = ref_as_integer(num, gen);
+        uint64_t v = ref_as_integer(num, static_cast<pdf_gennum>(gen));
         ref_map[k] = v;
     }
     if (c > 0) replace_font_references(self, ref_map);
@@ -341,7 +341,7 @@ merge_fonts(PDFDoc *self, PyObject *args) {
         const char *data, *tounicode_data;
         Py_ssize_t sz, tounicode_sz;
         if (!PyArg_ParseTuple(PyTuple_GET_ITEM(items, i), "(ll)(ll)O!O!s#s#", &num, &gen, &t0num, &t0gen, &PyList_Type, &W, &PyList_Type, &W2, &data, &sz, &tounicode_data, &tounicode_sz)) return NULL;
-        PdfReference ref(num, gen);
+        PdfReference ref(num, static_cast<pdf_gennum>(gen));
         PdfObject *font = objects.GetObject(ref);
         if (font) {
             if (PyObject_IsTrue(W)) {
@@ -362,7 +362,7 @@ merge_fonts(PDFDoc *self, PyObject *args) {
             }
         }
         if (tounicode_sz) {
-            PdfObject *t0font = objects.GetObject(PdfReference(t0num, t0gen));
+            PdfObject *t0font = objects.GetObject(PdfReference(t0num, static_cast<pdf_gennum>(t0gen)));
             if (t0font) {
                 PdfObject *s = t0font->GetIndirectKey("ToUnicode");
                 if (!s) { PyErr_SetString(PyExc_ValueError, "Type0 font has no ToUnicode stream"); return NULL; }
diff --git a/src/calibre/utils/podofo/images.cpp b/src/calibre/utils/podofo/images.cpp
index fddb21b4b7..fcde85d2c5 100644
--- a/src/calibre/utils/podofo/images.cpp
+++ b/src/calibre/utils/podofo/images.cpp
@@ -97,7 +97,7 @@ dedup_images(PDFDoc *self, PyObject *args) {
                             const PdfReference &r = ref_map.at(x.second->GetReference());
                             new_xobject.AddKey(x.first.GetName(), r);
                             changed = true;
-                        } catch (const std::out_of_range &err) { continue; }
+                        } catch (const std::out_of_range &err) { (void)err; continue; }
                     }
                 }
                 if (changed) resources.AddKey("XObject", new_xobject);
diff --git a/src/calibre/utils/podofo/outline.cpp b/src/calibre/utils/podofo/outline.cpp
index 134198dc0e..42c6c7b810 100644
--- a/src/calibre/utils/podofo/outline.cpp
+++ b/src/calibre/utils/podofo/outline.cpp
@@ -61,7 +61,7 @@ create(PDFOutlineItem *self, PyObject *args) {
         PdfString title = podofo_convert_pystring(title_buf);
         try {
             page = self->doc->GetPage(num - 1);
-        } catch(const PdfError &err) { page = NULL; }
+        } catch(const PdfError &err) { (void)err; page = NULL; }
         if (page == NULL) { PyErr_Format(PyExc_ValueError, "Invalid page number: %u", num); goto error; }
         PdfDestination dest(page, left, top, zoom);
         if (PyObject_IsTrue(as_child)) {