diff --git a/packages/margo/package.py b/packages/margo/package.py
index f6649b9fff02fde722ddbf839759f9e2b33e5fa4..f512d98436bbac7a3fa19ce7bb34fcdfaf3ae6be 100644
--- a/packages/margo/package.py
+++ b/packages/margo/package.py
@@ -35,6 +35,7 @@ class Margo(AutotoolsPackage):
     version('develop', branch='master')
     version('0.4', tag='v0.4', preferred=True)
 
+    depends_on('mercury@develop', when='@develop', type=("build", "link", "run"))
     depends_on('mercury@1.0.0:', type=("build", "link", "run"))
     depends_on('argobots@develop')
     depends_on('autoconf@2.65:', type=("build"))