diff --git a/pkgs/development/python-modules/yaswfp/default.nix b/pkgs/development/python-modules/yaswfp/default.nix
index 6ed211dd9a0b..6d0b1f447c34 100644
--- a/pkgs/development/python-modules/yaswfp/default.nix
+++ b/pkgs/development/python-modules/yaswfp/default.nix
@@ -8,7 +8,7 @@
 
 buildPythonPackage (finalAttrs: {
   pname = "yaswfp";
-  version = "0.9.3-unstable-20210331";
+  version = "0.9.3-unstable-2014-09-11";
   pyproject = true;
 
   __structuredAttrs = true;