diff --git a/pkgs/development/python-modules/dask/default.nix b/pkgs/development/python-modules/dask/default.nix
index d69ae77e1a6..2a088706f6c 100644
--- a/pkgs/development/python-modules/dask/default.nix
+++ b/pkgs/development/python-modules/dask/default.nix
@@ -32,8 +32,6 @@ buildPythonPackage rec {
     pytest_xdist # takes >10mins to run single-threaded
   ];
 
-  pytestFlagsArray = [ "-n $NIX_BUILD_CORES" ];
-
   dontUseSetuptoolsCheck = true;
 
   propagatedBuildInputs = [
@@ -56,6 +54,13 @@ buildPythonPackage rec {
       --replace "cmdclass=versioneer.get_cmdclass()," ""
   '';
 
+  # dask test suite with consistently fail when using high core counts
+  preCheck = ''
+    NIX_BUILD_CORES=$((NIX_BUILD_CORES > 8 ? 8 : NIX_BUILD_CORES))
+  '';
+
+  pytestFlagsArray = [ "-n $NIX_BUILD_CORES" ];
+
   disabledTests = [
     "test_argwhere_str"
     "test_count_nonzero_str"