diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index b95f43e9016f39f3432210b14776bb5c94315e32..86eaa3bb9149e86b1afa335eeb237d4fbe5a79d6 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -449,6 +449,9 @@ def __str__(self):
     def __repr__(self):
         return str(self)
 
+    def __contains__(self, string):
+        return string in str(self)
+
 
 @key_ordering
 class CompilerSpec(object):