diff --git a/kitty/fonts.c b/kitty/fonts.c
index b6c4c7b9a..04950df43 100644
--- a/kitty/fonts.c
+++ b/kitty/fonts.c
@@ -176,7 +176,7 @@ font_group_for(double font_sz_in_pts, double logical_dpi_x, double logical_dpi_y
 
 static inline void
 clear_canvas(FontGroup *fg) {
-    if (fg->canvas) memset(fg->canvas, 0, CELLS_IN_CANVAS * fg->cell_width * fg->cell_height * sizeof(pixel));
+    if (fg->canvas) memset(fg->canvas, 0, sizeof(pixel) * CELLS_IN_CANVAS * fg->cell_width * fg->cell_height);
 }
 
 
@@ -1388,7 +1388,7 @@ concat_cells(PyObject UNUSED *self, PyObject *args) {
     PyObject *cells;
     if (!PyArg_ParseTuple(args, "IIpO!", &cell_width, &cell_height, &is_32_bit, &PyTuple_Type, &cells)) return NULL;
     size_t num_cells = PyTuple_GET_SIZE(cells), r, c, i;
-    PyObject *ans = PyBytes_FromStringAndSize(NULL, 4 * cell_width * cell_height * num_cells);
+    PyObject *ans = PyBytes_FromStringAndSize(NULL, (size_t)4 * cell_width * cell_height * num_cells);
     if (ans == NULL) return PyErr_NoMemory();
     pixel *dest = (pixel*)PyBytes_AS_STRING(ans);
     for (r = 0; r < cell_height; r++) {
diff --git a/kitty/freetype.c b/kitty/freetype.c
index 80403a4ad..43fbb1f5c 100644
--- a/kitty/freetype.c
+++ b/kitty/freetype.c
@@ -457,7 +457,7 @@ downsample_bitmap(ProcessedBitmap *bm, unsigned int width, unsigned int cell_hei
     // it matters
     float ratio = MAX((float)bm->width / width, (float)bm->rows / cell_height);
     int factor = (int)ceilf(ratio);
-    uint8_t *dest = calloc(4, width * cell_height);
+    uint8_t *dest = calloc(4, (size_t)width * cell_height);
     if (dest == NULL) fatal("Out of memory");
     uint8_t *d = dest;
 
diff --git a/kitty/glfw.c b/kitty/glfw.c
index 961fa4870..72208ae71 100644
--- a/kitty/glfw.c
+++ b/kitty/glfw.c
@@ -1079,7 +1079,7 @@ set_custom_cursor(PyObject *self UNUSED, PyObject *args) {
     size_t count = MIN((size_t)PyTuple_GET_SIZE(images), arraysz(gimages));
     for (size_t i = 0; i < count; i++) {
         if (!PyArg_ParseTuple(PyTuple_GET_ITEM(images, i), "s#ii", &gimages[i].pixels, &sz, &gimages[i].width, &gimages[i].height)) return NULL;
-        if (gimages[i].width * gimages[i].height * 4 != sz) {
+        if ((Py_ssize_t)gimages[i].width * gimages[i].height * 4 != sz) {
             PyErr_SetString(PyExc_ValueError, "The image data size does not match its width and height");
             return NULL;
         }