diff --git a/pkgs/development/python-modules/ray/default.nix b/pkgs/development/python-modules/ray/default.nix
index c6b764181875..99a62a64025d 100644
--- a/pkgs/development/python-modules/ray/default.nix
+++ b/pkgs/development/python-modules/ray/default.nix
@@ -68,7 +68,7 @@ buildPythonPackage rec {
   src =
     let
       pyShortVersion = "cp${builtins.replaceStrings ["."] [""] python.pythonVersion}";
-      binary-hash = (import ./binary-hashes.nix)."${pyShortVersion}";
+      binary-hash = (import ./binary-hashes.nix)."${pyShortVersion}" or {};
     in
     fetchPypi ({
       inherit pname version format;
diff --git a/pkgs/development/python-modules/tensorflow/bin.nix b/pkgs/development/python-modules/tensorflow/bin.nix
index dcfa8e0e964c..c9ed92712166 100644
--- a/pkgs/development/python-modules/tensorflow/bin.nix
+++ b/pkgs/development/python-modules/tensorflow/bin.nix
@@ -57,7 +57,7 @@ in buildPythonPackage {
     platform = if stdenv.isDarwin then "mac" else "linux";
     unit = if cudaSupport then "gpu" else "cpu";
     key = "${platform}_py_${pyVerNoDot}_${unit}";
-  in fetchurl packages.${key};
+  in fetchurl (packages.${key} or {});
 
   propagatedBuildInputs = [
     astunparse