diff --git a/src/subcircuit/newSub.py b/src/subcircuit/newSub.py
index b452dafe3..6814fd2bc 100644
--- a/src/subcircuit/newSub.py
+++ b/src/subcircuit/newSub.py
@@ -54,7 +54,8 @@ def createSubcircuit(self, subName):
                 os.mkdir(self.schematic_path)
                 self.schematic = os.path.join(
                     self.schematic_path, self.create_schematic)
-                self.cmd = "eeschema " + self.schematic + ".sch"
+                # New KiCad v6 file extension
+                self.cmd = "eeschema " + self.schematic + ".kicad_sch"
                 self.obj_workThread = Worker.WorkerThread(self.cmd)
                 self.obj_workThread.start()
                 self.close()
diff --git a/src/subcircuit/openSub.py b/src/subcircuit/openSub.py
index 53c3cbf1f..03e0175d1 100644
--- a/src/subcircuit/openSub.py
+++ b/src/subcircuit/openSub.py
@@ -34,6 +34,12 @@ def body(self):
 
             self.schname = os.path.basename(self.editfile)
             self.editfile = os.path.join(self.editfile, self.schname)
-            self.cmd = "eeschema " + self.editfile + ".sch "
+
+            schematic_file = self.editfile + ".kicad_sch"  # kicad6 file
+            if not os.path.exists(schematic_file) and os.path.exists(
+                    self.editfile + ".sch"):
+                schematic_file = self.editfile + ".sch"    # kicad4 file
+
+            self.cmd = "eeschema " + schematic_file
             self.obj_workThread = WorkerThread(self.cmd)
             self.obj_workThread.start()