diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 12998682665a..ff3535c7c78d 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -3249,7 +3249,7 @@ 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 { };