diff --git a/modules/doc/install.rst b/modules/doc/install.rst
index b86672515a32ada004e5a40b97acd8750997f773..cfea868bf996b792f7942aff96324fa692ab73f7 100644
--- a/modules/doc/install.rst
+++ b/modules/doc/install.rst
@@ -205,7 +205,7 @@ can influence it.
     files directly)
   * `PNG_LIBRARY` defines the location of the libpng library (file name starting
     with `libpng`)
-  * `PNG_INCLUDE_DIR` defines the include folder of libpng (contains include
+  * `PNG_PNG_INCLUDE_DIR` defines the include folder of libpng (contains include
     files directly)
   * `ZLIB_LIBRARY` defines the location of the zlib library (file name starting
     with `libz`)
diff --git a/modules/gfx/src/CMakeLists.txt b/modules/gfx/src/CMakeLists.txt
index acd3f9eb4bf94f4fe29b2e4dccd863a0659f8ecc..d7790789e5c38d1bac5fcd90a29cba681aac1297 100644
--- a/modules/gfx/src/CMakeLists.txt
+++ b/modules/gfx/src/CMakeLists.txt
@@ -210,7 +210,7 @@ module(NAME gfx SOURCES ${OST_GFX_SOURCES} ${OST_GFX_MAP_SOURCES}
                ${OST_GFX_HEADERS} ${OST_GFX_MAP_HEADERS}
        DEPENDS_ON ${OST_GFX_DEPENDENCIES})
 
-include_directories(${PNG_INCLUDE_DIR} ${OPENGL_INCLUDE_DIR})
+include_directories(${PNG_INCLUDE_DIRS} ${OPENGL_INCLUDE_DIR})
 
 # link against OpenGL and PNG libraries
 target_link_libraries(ost_gfx ${OPENGL_LIBRARIES} ${PNG_LIBRARIES})