diff --git a/pkgs/development/python-modules/finalfusion/default.nix b/pkgs/development/python-modules/finalfusion/default.nix
index 18a8e5e56536..f079dbe77bc8 100644
--- a/pkgs/development/python-modules/finalfusion/default.nix
+++ b/pkgs/development/python-modules/finalfusion/default.nix
@@ -36,6 +36,10 @@ buildPythonPackage rec {
 
   postPatch = ''
     patchShebangs tests/integration
+
+    # `np.float` was a deprecated alias of the builtin `float`
+    substituteInPlace tests/test_storage.py \
+      --replace 'dtype=np.float)' 'dtype=float)'
   '';
 
   checkPhase = ''