diff --git a/pyproject.toml b/pyproject.toml
index d049066..541e62a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -20,7 +20,7 @@ requires-python = ">=3.8"
 dependencies = [
     "aiida-vibroscopy>=1.0.2",
     "aiida-phonopy>=1.1.3",
-    "phonopy=2.25.0",
+    "phonopy==2.25.0",
     "pre-commit",
     "euphonic",
     "kaleido",