diff --git a/src/pytest_amaranth_sim/plugin.py b/src/pytest_amaranth_sim/plugin.py
index 05e88a0..358930a 100644
--- a/src/pytest_amaranth_sim/plugin.py
+++ b/src/pytest_amaranth_sim/plugin.py
@@ -66,8 +66,19 @@ class SimulatorFixture:
             self.sim.add_process(p)
 
         if self.vcds:
-            with self.sim.write_vcd(self.name + ".vcd", self.name + ".gtkw"):
-                self.sim.run()
+            import amaranth.sim.pysim
+
+            old_close = amaranth.sim.pysim._VCDWriter.close
+            def my_close(vcd, ts):
+                old_close(vcd, self.sim._engine.now)
+
+            amaranth.sim.pysim._VCDWriter.close = my_close
+
+            try:
+                with self.sim.write_vcd(self.name + ".vcd", self.name + ".gtkw"):
+                    self.sim.run()
+            except AssertionError as e:
+                raise
         else:
             self.sim.run()