diff --git a/tools/ports/libpng.py b/tools/ports/libpng.py
index 63f0da0a8b716..60b2692a3bffb 100644
--- a/tools/ports/libpng.py
+++ b/tools/ports/libpng.py
@@ -39,6 +39,7 @@ def create(final):
     pnglibconf_h = os.path.join(os.path.dirname(__file__), 'libpng/pnglibconf.h')
     shutil.copyfile(pnglibconf_h, os.path.join(source_path, 'pnglibconf.h'))
     ports.install_headers(source_path)
+    ports.make_pkg_config('libpng', TAG, '-sUSE_LIBPNG')
 
     flags = ['-sUSE_ZLIB']
     if settings.PTHREADS:
diff --git a/tools/ports/zlib.py b/tools/ports/zlib.py
index 38cfa89da78f7..18e1c9e253ced 100644
--- a/tools/ports/zlib.py
+++ b/tools/ports/zlib.py
@@ -23,7 +23,7 @@ def create(final):
     zconf_h = os.path.join(os.path.dirname(__file__), 'zlib/zconf.h')
     shutil.copyfile(zconf_h, os.path.join(source_path, 'zconf.h'))
     ports.install_headers(source_path)
-    ports.make_pkg_config('zlib', VERSION, '-sUSE_ZIB')
+    ports.make_pkg_config('zlib', VERSION, '-sUSE_ZLIB')
 
     # build
     srcs = 'adler32.c compress.c crc32.c deflate.c gzclose.c gzlib.c gzread.c gzwrite.c infback.c inffast.c inflate.c inftrees.c trees.c uncompr.c zutil.c'.split()