diff --git a/spack/packages/madx/package.py b/spack/packages/madx/package.py
index 78d98350bef9171162b78970bd711c7259eae775..c80bd06b4b069338b66e700843b0cae928b47361 100644
--- a/spack/packages/madx/package.py
+++ b/spack/packages/madx/package.py
@@ -43,6 +43,7 @@ class Madx(CMakePackage):
     #variant('pythia8', default=False, description='Build the Pythia8-based examples')
 
     depends_on("libx11")
+    depends_on("zlib")
 
     # Build dependencies
     # FIXME: Use spack's autodiff package once there is one