diff --git a/pyproject.toml b/pyproject.toml
index 262dca9..fe24d34 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -24,7 +24,7 @@ dependencies = [
     "pyepics ~= 3.5, >=3.5.5",
     "pytest ~= 8.0",
     "h5py ~= 3.10",
-    "hdf5plugin ~= 4.3",
+    "hdf5plugin >=4.3, < 6.0",
 ]
 
 [project.optional-dependencies]