diff --git a/var/spack/repos/builtin/packages/silo/package.py b/var/spack/repos/builtin/packages/silo/package.py
index 3f234473b2b..1c8576bf96a 100644
--- a/var/spack/repos/builtin/packages/silo/package.py
+++ b/var/spack/repos/builtin/packages/silo/package.py
@@ -35,6 +35,7 @@ class Silo(AutotoolsPackage):
     variant('fpzip', default=True,
             description='Enable fpzip support')
 
+    depends_on('m4', type='build', when='+shared')
     depends_on('autoconf', type='build', when='+shared')
     depends_on('automake', type='build', when='+shared')
     depends_on('libtool', type='build', when='+shared')