diff --git a/changelog.d/143.fixed.md b/changelog.d/143.fixed.md
new file mode 100644
index 00000000..04399d58
--- /dev/null
+++ b/changelog.d/143.fixed.md
@@ -0,0 +1 @@
+Fixed add_port ignore keep_mirror flag
\ No newline at end of file
diff --git a/src/kfactory/kcell.py b/src/kfactory/kcell.py
index 662e6d43..7f923674 100644
--- a/src/kfactory/kcell.py
+++ b/src/kfactory/kcell.py
@@ -998,7 +998,7 @@ def add_port(
         """
         if self._locked:
             raise LockedError(self)
-        self.ports.add_port(port=port, name=name)
+        self.ports.add_port(port=port, name=name, keep_mirror=keep_mirror)
 
     def add_ports(
         self, ports: Iterable[Port], prefix: str = "", keep_mirror: bool = False
@@ -2243,10 +2243,10 @@ def add_port(
         """
         _port = port.copy()
         if not keep_mirror:
-            if port._trans:
-                port._trans.mirror = False
-            elif port._dcplx_trans:
-                port._dcplx_trans.mirror = False
+            if _port._trans:
+                _port._trans.mirror = False
+            elif _port._dcplx_trans:
+                _port._dcplx_trans.mirror = False
         if name is not None:
             _port.name = name
         self._ports.append(_port)
@@ -2257,7 +2257,7 @@ def add_ports(
         """Append a list of ports."""
         for p in ports:
             name = p.name or ""
-            self.add_port(port=p, name=prefix + name)
+            self.add_port(port=p, name=prefix + name, keep_mirror=keep_mirror)
 
     @overload
     def create_port(
diff --git a/tests/test_ports.py b/tests/test_ports.py
index 573e6ba1..5143300f 100644
--- a/tests/test_ports.py
+++ b/tests/test_ports.py
@@ -100,3 +100,41 @@ def test_connect_integer(wg):
     wg2.connect("o1", wg1, "o1")
 
     assert wg2.ports["o1"].trans == kf.kdb.Trans(0, False, 0, 0)
+
+
+def test_keep_mirror(LAYER):
+    c = kf.KCell()
+
+    p1 = kf.Port(trans=kf.kdb.Trans.M90, width=1000, layer=LAYER.WG)
+
+    c.add_port(p1, name="o1")
+    c.add_port(p1, name="o2", keep_mirror=True)
+
+    assert c["o1"].trans.is_mirror() is False
+    assert c["o2"].trans.is_mirror() is True
+
+
+def test_addports_keep_mirror(LAYER):
+    c = kf.KCell()
+
+    ports = [
+        kf.Port(
+            name=f"{i}",
+            width=1000,
+            layer=LAYER.WG,
+            trans=kf.kdb.Trans(i, True, 0, 0),
+        )
+        for i in range(4)
+    ]
+
+    c.add_ports(ports, prefix="mirr_", keep_mirror=True)
+    c.add_ports(ports, prefix="nomirr_", keep_mirror=False)
+
+    for i in range(4):
+        t1 = c[f"mirr_{i}"].trans
+        t2 = c[f"nomirr_{i}"].trans
+
+        t2_mirr = t2.dup()
+        t2_mirr.mirror = not t2_mirr.is_mirror()
+
+        assert t1 == t2_mirr