diff --git a/pkgs/by-name/ta/tandoor-recipes/package.nix b/pkgs/by-name/ta/tandoor-recipes/package.nix
index 8e7e30985e83..ebc3e3fec08d 100644
--- a/pkgs/by-name/ta/tandoor-recipes/package.nix
+++ b/pkgs/by-name/ta/tandoor-recipes/package.nix
@@ -22,6 +22,11 @@ python.pkgs.buildPythonPackage {
   ];
 
   postPatch = ''
+    # high parallelism let the tests easily fail with concurrent errors
+    if (( $NIX_BUILD_CORES > 4)); then
+      NIX_BUILD_CORES=4
+    fi
+
     substituteInPlace pytest.ini --subst-var NIX_BUILD_CORES
   '';