diff --git a/packages/arbor/package.py b/packages/arbor/package.py
index e02ea5b4154be3a0c45ee4f3717a9e84ec96caca..9b0cb883f320b0c2fb75b8ff2d2446e2e6126e66 100644
--- a/packages/arbor/package.py
+++ b/packages/arbor/package.py
@@ -89,7 +89,7 @@ class Arbor(CMakePackage, CudaPackage):
         depends_on("cuda@11:", when="@0.7.1:")
 
     # mpi
-    depends_on("mpi", when="+mpi")
+    depends_on("mpi", when="+mpi", type=("build", "run"))
     depends_on("py-mpi4py", when="+mpi+python", type=("build", "run"))
 
     # python (bindings)