diff --git a/setup.py b/setup.py
index 28116d6..b154803 100644
--- a/setup.py
+++ b/setup.py
@@ -42,7 +42,7 @@ setup(
     install_requires=[
         "importlib_metadata; python_version<'3.8'",  # for __version__ and amaranth._toolchain.yosys
         "importlib_resources; python_version<'3.9'", # for amaranth._toolchain.yosys
-        "pyvcd~=0.2.2", # for amaranth.pysim
+        "pyvcd>=0.2.2,<0.4", # for amaranth.pysim
         "Jinja2~=3.0",  # for amaranth.build
     ],
     extras_require={