diff --git a/pyproject.toml b/pyproject.toml
index 9df4448..4b07166 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,7 +7,7 @@ dependencies = [
     "brotli",
     "CairoSVG",
     "chevron",
-    "cocotb",
+    "cocotb==1.8.0",
     "gdstk",
     "GitPython",
     "klayout<0.30.0,>=0.29.0",
diff --git a/requirements.txt b/requirements.txt
index 867292d..8df3389 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -24,7 +24,7 @@ chevron==0.14.0
     # via tt-support-tools (pyproject.toml)
 click==8.1.7
     # via yowasp-yosys
-cocotb==1.9.2
+cocotb==1.8.0
     # via tt-support-tools (pyproject.toml)
 contourpy==1.3.3
     # via matplotlib