diff --git a/var/spack/repos/builtin/packages/m4/package.py b/var/spack/repos/builtin/packages/m4/package.py
index cb0091e6e1a..a4599c3afc1 100644
--- a/var/spack/repos/builtin/packages/m4/package.py
+++ b/var/spack/repos/builtin/packages/m4/package.py
@@ -44,6 +44,7 @@ class M4(AutotoolsPackage, GNUMirrorPackage):
     variant('sigsegv', default=True,
             description="Build the libsigsegv dependency")
 
+    depends_on('diffutils', type='build')
     depends_on('libsigsegv', when='+sigsegv')
 
     build_directory = 'spack-build'