diff --git a/pyproject.toml b/pyproject.toml
index 3fdb7911..08358095 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -49,7 +49,7 @@ gui = [
     "Gooey>=1.0.8.1,<1.1"
 ]
 doc = [
-    "matplotlib>=3.5.1,<3.8",
+    "matplotlib>=3.5.1,<3.9",
     "myst-nb>=0.13.2,<0.18",
     "sphinx>=5.2.0,<7.3",
     "sphinxcontrib-httpdomain>=1.7.0,<1.9",