diff --git a/kitty/graphics.c b/kitty/graphics.c
index 33dff46a5..40b54a16b 100644
--- a/kitty/graphics.c
+++ b/kitty/graphics.c
@@ -842,8 +842,8 @@ grman_handle_command(GraphicsManager *self, const GraphicsCommand *g, const uint
         case 't':
         case 'T':
         case 'q':
-            iid = g->id;
-            if (g->action == 'q') { q_iid = iid; iid = 0; if (!q_iid) { REPORT_ERROR("Query graphics command without image id"); break; } }
+            iid = g->id; q_iid = iid;
+            if (g->action == 'q') { iid = 0; if (!q_iid) { REPORT_ERROR("Query graphics command without image id"); break; } }
             image = handle_add_command(self, g, payload, is_dirty, iid);
             ret = create_add_response(self, image != NULL, g->action == 'q' ? q_iid: self->last_init_graphics_command.id);
             if (self->last_init_graphics_command.action == 'T' && image && image->data_loaded) handle_put_command(self, &self->last_init_graphics_command, c, is_dirty, image);
diff --git a/kitty/mouse.c b/kitty/mouse.c
index b327792c5..766767313 100644
--- a/kitty/mouse.c
+++ b/kitty/mouse.c
@@ -163,7 +163,7 @@ detect_url(Window *w, Screen *screen, unsigned int x, unsigned int y) {
 
 
 HANDLER(handle_move_event) {
-    unsigned int x, y;
+    unsigned int x = 0, y = 0;
     if (OPT(focus_follows_mouse)) {
         Tab *t = global_state.tabs + global_state.active_tab;
         if (window_idx != t->active_window) {
@@ -327,7 +327,7 @@ void
 mouse_event(int button, int modifiers) {
     MouseShape old_cursor = mouse_cursor_shape;
     bool in_tab_bar;
-    unsigned int window_idx;
+    unsigned int window_idx = 0;
     Window *w = window_for_event(&window_idx, &in_tab_bar);
     if (in_tab_bar) { 
         mouse_cursor_shape = HAND;
@@ -346,7 +346,7 @@ scroll_event(double UNUSED xoffset, double yoffset) {
     if (s == 0) return;
     bool upwards = s > 0;
     bool in_tab_bar;
-    unsigned int window_idx;
+    unsigned int window_idx = 0;
     Window *w = window_for_event(&window_idx, &in_tab_bar);
     if (w) {
         Screen *screen = w->render_data.screen;
diff --git a/kitty/screen.c b/kitty/screen.c
index c96fff9c7..35697edae 100644
--- a/kitty/screen.c
+++ b/kitty/screen.c
@@ -140,7 +140,7 @@ screen_resize(Screen *self, unsigned int lines, unsigned int columns) {
 
     bool is_main = self->linebuf == self->main_linebuf;
     index_type num_content_lines_before, num_content_lines_after;
-    index_type num_content_lines;
+    index_type num_content_lines = 0;
 
     // Resize main linebuf
     HistoryBuf *nh = realloc_hb(self->historybuf, self->historybuf->ynum, columns);
diff --git a/setup.py b/setup.py
index 0d0914b56..af5003e67 100755
--- a/setup.py
+++ b/setup.py
@@ -130,7 +130,10 @@ def init_env(
     missing_braces = ''
     if ccver < (5, 2) and cc == 'gcc':
         missing_braces = '-Wno-missing-braces'
-    optimize = '-g3' if debug or sanitize else '-O3'
+    df = '-g3'
+    if ccver >= (5, 0):
+        df += ' -Og'
+    optimize = df if debug or sanitize else '-O3'
     sanitize_args = get_sanitize_args(cc, ccver) if sanitize else set()
     cflags = os.environ.get(
         'OVERRIDE_CFLAGS', (