diff --git a/var/spack/repos/builtin/packages/dealii/package.py b/var/spack/repos/builtin/packages/dealii/package.py
index 902e310be6..b4cade21df 100644
--- a/var/spack/repos/builtin/packages/dealii/package.py
+++ b/var/spack/repos/builtin/packages/dealii/package.py
@@ -591,6 +591,9 @@ def cmake_args(self):
                     self.define("SCALAPACK_FOUND", True),
                     self.define("SCALAPACK_INCLUDE_DIRS", spec["scalapack"].prefix.include),
                     self.define("SCALAPACK_LIBRARIES", scalapack_libs.joined(";")),
+                    # If SCALAPACK_LIBRARY is not set, deal.II still searches
+                    # for SCALAPACK despite the above settings:
+                    self.define("SCALAPACK_LIBRARY", scalapack_libs.joined(";")),
                 ]
             )
 
diff --git a/var/spack/repos/builtin/packages/sundials/package.py b/var/spack/repos/builtin/packages/sundials/package.py
index d345bb793b..4b22721a41 100644
--- a/var/spack/repos/builtin/packages/sundials/package.py
+++ b/var/spack/repos/builtin/packages/sundials/package.py
@@ -452,9 +452,9 @@ def cmake_args(self):
         if "+magma" in spec:
             args.extend([define("ENABLE_MAGMA", True), define("MAGMA_DIR", spec["magma"].prefix)])
             if "+cuda" in spec:
-                define("SUNDIALS_MAGMA_BACKENDS", "CUDA")
+                args.extend([define("SUNDIALS_MAGMA_BACKENDS", "CUDA")])
             if "+rocm" in spec:
-                define("SUNDIALS_MAGMA_BACKENDS", "HIP")
+                args.extend([define("SUNDIALS_MAGMA_BACKENDS", "HIP")])
 
         # Building with PETSc
         if "+petsc" in spec: