diff --git a/pkgs/by-name/bl/blas/package.nix b/pkgs/by-name/bl/blas/package.nix
index 01ad1839c339..85e2e2cb3412 100644
--- a/pkgs/by-name/bl/blas/package.nix
+++ b/pkgs/by-name/bl/blas/package.nix
@@ -3,6 +3,7 @@
   stdenv,
   lapack-reference,
   openblas,
+  mpiCheckPhaseHook,
   isILP64 ? false,
   blasProvider ? openblas,
 }:
@@ -186,6 +187,10 @@ stdenv.mkDerivation {
     "dev"
   ];
 
+  propagatedBuildInputs = [
+    mpiCheckPhaseHook
+  ];
+
   meta = (blasProvider'.meta or { }) // {
     description = "${lib.getName blasProvider} with just the BLAS C and FORTRAN ABI";
   };
diff --git a/pkgs/development/python-modules/numpy/2.nix b/pkgs/development/python-modules/numpy/2.nix
index 67c60475fd5f..0fc2a30f3555 100644
--- a/pkgs/development/python-modules/numpy/2.nix
+++ b/pkgs/development/python-modules/numpy/2.nix
@@ -91,7 +91,6 @@ buildPythonPackage (finalAttrs: {
   # see https://github.com/OpenMathLib/OpenBLAS/issues/2993
   preConfigure = ''
     sed -i 's/-faltivec//' numpy/distutils/system_info.py
-    export OMP_NUM_THREADS=$((NIX_BUILD_CORES > 64 ? 64 : NIX_BUILD_CORES))
   '';
 
   buildInputs = [
diff --git a/pkgs/development/python-modules/scipy/default.nix b/pkgs/development/python-modules/scipy/default.nix
index cdecd986e4ef..30999320f1e8 100644
--- a/pkgs/development/python-modules/scipy/default.nix
+++ b/pkgs/development/python-modules/scipy/default.nix
@@ -190,11 +190,6 @@ buildPythonPackage (finalAttrs: {
   '';
 
   preCheck = ''
-    export OMP_NUM_THREADS=$(( $NIX_BUILD_CORES / 4 ))
-    if [ $OMP_NUM_THREADS -eq 0 ]; then
-      export OMP_NUM_THREADS=1
-    fi
-
     cd $out
   '';