diff --git a/var/spack/repos/builtin/packages/plumed/package.py b/var/spack/repos/builtin/packages/plumed/package.py
index c8b1f8e9b96..a3f62ac38a3 100644
--- a/var/spack/repos/builtin/packages/plumed/package.py
+++ b/var/spack/repos/builtin/packages/plumed/package.py
@@ -68,6 +68,7 @@ class Plumed(AutotoolsPackage):
     depends_on('autoconf', type='build')
     depends_on('automake', type='build')
     depends_on('libtool', type='build')
+    depends_on('py-cython', type='build', when='@2.5:')
 
     force_autoreconf = True