diff --git a/src/nvim/main.c b/src/nvim/main.c
index ae64046d07..f79fb57eae 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -313,6 +313,26 @@ int main(int argc, char **argv)
     input_start(STDIN_FILENO);
   }
 
+  // Wait for UIs to set up Nvim or show early messages
+  // and prompts (--cmd, swapfile dialog, …).
+  bool use_remote_ui = (embedded_mode && !headless_mode);
+  bool use_builtin_ui = (!headless_mode && !embedded_mode && !silent_mode);
+  if (use_remote_ui || use_builtin_ui) {
+    TIME_MSG("waiting for UI");
+    if (use_remote_ui) {
+      remote_ui_wait_for_attach();
+    } else {
+      ui_builtin_start();
+    }
+    TIME_MSG("done waiting for UI");
+
+    // prepare screen now, so external UIs can display messages
+    starting = NO_BUFFERS;
+    screenclear();
+    TIME_MSG("initialized screen early for UI");
+  }
+
+
   // open terminals when opening files that start with term://
 #define PROTO "term://"
   do_cmdline_cmd("augroup nvim_terminal");
@@ -335,25 +355,6 @@ int main(int argc, char **argv)
     p_lpl = false;
   }
 
-  // Wait for UIs to set up Nvim or show early messages
-  // and prompts (--cmd, swapfile dialog, …).
-  bool use_remote_ui = (embedded_mode && !headless_mode);
-  bool use_builtin_ui = (!headless_mode && !embedded_mode && !silent_mode);
-  if (use_remote_ui || use_builtin_ui) {
-    TIME_MSG("waiting for UI");
-    if (use_remote_ui) {
-      remote_ui_wait_for_attach();
-    } else {
-      ui_builtin_start();
-    }
-    TIME_MSG("done waiting for UI");
-
-    // prepare screen now, so external UIs can display messages
-    starting = NO_BUFFERS;
-    screenclear();
-    TIME_MSG("initialized screen early for UI");
-  }
-
   // Execute --cmd arguments.
   exe_pre_commands(&params);
 
diff --git a/test/functional/core/startup_spec.lua b/test/functional/core/startup_spec.lua
index 394eb73187..9b0668f9e6 100644
--- a/test/functional/core/startup_spec.lua
+++ b/test/functional/core/startup_spec.lua
@@ -358,6 +358,31 @@ describe('sysinit', function()
     eq('loaded 1 xdg 0 vim 1',
        eval('printf("loaded %d xdg %d vim %d", g:loaded, get(g:, "xdg", 0), get(g:, "vim", 0))'))
   end)
+
+  it('fixed hang issue with -D (#12647)', function()
+    local screen
+    screen = Screen.new(60, 6)
+    screen:attach()
+    command([[let g:id = termopen('"]]..nvim_prog..
+    [[" -u NONE -i NONE --cmd "set noruler" -D')]])
+    screen:expect([[
+      ^                                                            |
+      Entering Debug mode.  Type "cont" to continue.              |
+      cmd: augroup nvim_terminal                                  |
+      >                                                           |
+      <" -u NONE -i NONE --cmd "set noruler" -D 1,0-1          All|
+                                                                  |
+    ]])
+    command([[call chansend(g:id, "cont\n")]])
+    screen:expect([[
+      ^                                                            |
+      ~                                                           |
+      [No Name]                                                   |
+                                                                  |
+      <" -u NONE -i NONE --cmd "set noruler" -D 1,0-1          All|
+                                                                  |
+    ]])
+  end)
 end)
 
 describe('clean', function()