diff --git a/kitty/boss.py b/kitty/boss.py
index 26ec4e6c8..9ae6f4b4c 100644
--- a/kitty/boss.py
+++ b/kitty/boss.py
@@ -507,9 +507,9 @@ def serialize_state_as_session(self) -> Iterator[str]:
         def skey(os_window_id: int) -> int:
             return s.get(os_window_id, 0)
 
-        for os_window_id in sorted(self.os_window_map, key=skey):
+        for i, os_window_id in enumerate(sorted(self.os_window_map, key=skey)):
             tm = self.os_window_map[os_window_id]
-            yield from tm.serialize_state_as_session()
+            yield from tm.serialize_state_as_session(is_first=i==0)
 
     @property
     def all_tab_managers(self) -> Iterator[TabManager]:
diff --git a/kitty/tabs.py b/kitty/tabs.py
index 8bf9a26fd..8fc308f87 100644
--- a/kitty/tabs.py
+++ b/kitty/tabs.py
@@ -1186,7 +1186,7 @@ def serialize_state(self) -> dict[str, Any]:
             'active_tab_idx': self.active_tab_idx,
         }
 
-    def serialize_state_as_session(self) -> list[str]:
+    def serialize_state_as_session(self, is_first: bool = False) -> list[str]:
         ans = []
         hmap = {tab_id: i for i, tab_id in enumerate(self.active_tab_history)}
         at = self.active_tab
@@ -1197,7 +1197,7 @@ def skey(tab: Tab) -> int:
         for tab in sorted(self, key=skey):
             ans.extend(tab.serialize_state_as_session())
         if ans:
-            prefix = ['new_os_window']
+            prefix = [] if is_first else ['new_os_window']
             if self.wm_class:
                 prefix.append(f'os_window_class {self.wm_class}')
             if self.wm_name: