diff --git a/mingw-nsis.spec b/mingw-nsis.spec
index 1be2f66..eff3568 100644
--- a/mingw-nsis.spec
+++ b/mingw-nsis.spec
@@ -21,6 +21,8 @@ BuildRequires:  mingw32-gcc-c++
 BuildRequires:  mingw32-binutils
 BuildRequires:  python
 BuildRequires:  scons
+BuildRequires:  zlib-devel
+BuildRequires:  mingw32-zlib
 
 # Don't build NSIS Menu as it doesn't actually work on POSIX systems: 1. it
 # doesn't find its index.html file without patching, 2. it has various links to