diff --git a/kitty/fonts.c b/kitty/fonts.c
index c5d2e83cc..0338fbba7 100644
--- a/kitty/fonts.c
+++ b/kitty/fonts.c
@@ -1118,9 +1118,17 @@ initialize_font_group(FontGroup *fg) {
     }
 #undef I
     calc_cell_metrics(fg);
-    fg->sprite_map = alloc_sprite_map(fg->cell_width, fg->cell_height);
-    if (!fg->sprite_map) fatal("Out of memory allocating a sprite map");
-    send_prerendered_sprites(fg);
+}
+
+
+void
+send_prerendered_sprites_for_window(OSWindow *w) {
+    FontGroup *fg = (FontGroup*)w->fonts_data;
+    if (!fg->sprite_map) {
+        fg->sprite_map = alloc_sprite_map(fg->cell_width, fg->cell_height);
+        if (!fg->sprite_map) fatal("Out of memory allocating a sprite map");
+        send_prerendered_sprites(fg);
+    }
 }
 
 FONTS_DATA_HANDLE
@@ -1269,6 +1277,7 @@ create_test_font_group(PyObject *self UNUSED, PyObject *args) {
     double sz, dpix, dpiy;
     if (!PyArg_ParseTuple(args, "ddd", &sz, &dpix, &dpiy)) return NULL;
     FontGroup *fg = font_group_for(sz, dpix, dpiy);
+    if (!fg->sprite_map) send_prerendered_sprites(fg);
     return Py_BuildValue("II", fg->cell_width, fg->cell_height);
 }
 
diff --git a/kitty/glfw.c b/kitty/glfw.c
index f1389b859..d85c68979 100644
--- a/kitty/glfw.c
+++ b/kitty/glfw.c
@@ -431,6 +431,7 @@ create_os_window(PyObject UNUSED *self, PyObject *args) {
     }
     w->logical_dpi_x = dpi_x; w->logical_dpi_y = dpi_y;
     w->fonts_data = fonts_data;
+    send_prerendered_sprites_for_window(w);
     if (logo.pixels && logo.width && logo.height) glfwSetWindowIcon(glfw_window, 1, &logo);
     glfwSetCursor(glfw_window, standard_cursor);
     update_os_window_viewport(w, false);
diff --git a/kitty/state.c b/kitty/state.c
index 49477cda7..c0b946166 100644
--- a/kitty/state.c
+++ b/kitty/state.c
@@ -628,6 +628,7 @@ PYWRAP1(os_window_font_size) {
             os_window->font_sz_in_pts = new_sz;
             os_window->fonts_data = NULL;
             os_window->fonts_data = load_fonts_data(os_window->font_sz_in_pts, os_window->logical_dpi_x, os_window->logical_dpi_y);
+            send_prerendered_sprites_for_window(os_window);
             resize_screen(os_window, os_window->tab_bar_render_data.screen, false);
             for (size_t ti = 0; ti < os_window->num_tabs; ti++) {
                 Tab *tab = os_window->tabs + ti;
diff --git a/kitty/state.h b/kitty/state.h
index 61e9e1055..8b4ca9e00 100644
--- a/kitty/state.h
+++ b/kitty/state.h
@@ -187,3 +187,4 @@ void send_image_to_gpu(uint32_t*, const void*, int32_t, int32_t, bool, bool);
 void send_sprite_to_gpu(FONTS_DATA_HANDLE fg, unsigned int, unsigned int, unsigned int, pixel*);
 void set_titlebar_color(OSWindow *w, color_type color);
 FONTS_DATA_HANDLE load_fonts_data(double, double, double);
+void send_prerendered_sprites_for_window(OSWindow *w);