diff --git a/var/spack/repos/builtin/packages/slate/package.py b/var/spack/repos/builtin/packages/slate/package.py
index f8b33d73726..67264d3bc92 100644
--- a/var/spack/repos/builtin/packages/slate/package.py
+++ b/var/spack/repos/builtin/packages/slate/package.py
@@ -27,6 +27,7 @@ class Slate(Package):
 
     depends_on('cuda@9:', when='+cuda')
     depends_on('intel-mkl')
+    depends_on('mercurial', type='build')
     depends_on('mpi', when='+mpi')
 
     conflicts('%gcc@:5')