diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index e2e5be60d40a..96ab5d1ed5cb 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -3247,7 +3247,7 @@ with pkgs;
   keystone = callPackage ../development/libraries/keystone { };
 
   casync = callPackage ../applications/networking/sync/casync {
-    sphinx = python3Packages.sphinx;
+    sphinx = buildPackages.python3Packages.sphinx;
   };
 
   cataract          = callPackage ../applications/misc/cataract { };