diff --git a/var/spack/repos/builtin/packages/libpng/package.py b/var/spack/repos/builtin/packages/libpng/package.py
index e02b08663e099e092e6f108227164e5e9648f73f..73c8c6234149839b7fc82312698d31aa5a0f6210 100644
--- a/var/spack/repos/builtin/packages/libpng/package.py
+++ b/var/spack/repos/builtin/packages/libpng/package.py
@@ -9,6 +9,8 @@ class Libpng(Package):
     version('1.6.15', '829a256f3de9307731d4f52dc071916d')
     version('1.6.14', '2101b3de1d5f348925990f9aa8405660')
 
+    depends_on('zlib')
+
     def install(self, spec, prefix):
         configure("--prefix=%s" % prefix)
         make()