diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index d18843c..a9df1fb 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -8,11 +8,6 @@ if(NOT CMAKE_BUILD_TYPE)
 	set(CMAKE_BUILD_TYPE Release)
 endif()
 
-# Check that submodules are present only if source was downloaded with git
-if(EXISTS "${CMAKE_SOURCE_DIR}/../.git" AND NOT EXISTS "${CMAKE_SOURCE_DIR}/../src/libpng/README")
-    message (FATAL_ERROR "Submodules are not initialized. Run \n\tgit submodule update --init --recursive\n within the repository")
-endif()
-
 add_executable(ect
 	main.cpp
 	gztools.cpp
@@ -56,7 +51,6 @@ add_subdirectory(lodepng EXCLUDE_FROM_ALL)
 add_subdirectory(miniz EXCLUDE_FROM_ALL)
 add_subdirectory(zlib EXCLUDE_FROM_ALL)
 add_subdirectory(zopfli EXCLUDE_FROM_ALL)
-file(COPY ${CMAKE_SOURCE_DIR}/pngusr.h DESTINATION ${CMAKE_SOURCE_DIR}/libpng/)
 add_subdirectory(optipng EXCLUDE_FROM_ALL)
 # Mozjpeg changes the install prefix if it thinks the current is defaulted
 set(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT FALSE)
diff --git a/src/Makefile b/src/Makefile
index cc24367..7aa9f0a 100755
--- a/src/Makefile
+++ b/src/Makefile
@@ -18,7 +18,7 @@ CXXSRC = support.cpp zopflipng.cpp zopfli/deflate.cpp zopfli/zopfli_gzip.cpp zop
 lodepng/lodepng.cpp lodepng/lodepng_util.cpp optipng/codec.cpp optipng/optipng.cpp jpegtran.cpp gztools.cpp \
 leanify/zip.cpp leanify/leanify.cpp
 
-.PHONY: libpng mozjpeg deps bin all install
+.PHONY: mozjpeg deps bin all install
 all: deps bin
 
 bin: deps
@@ -33,9 +33,6 @@ libz.a:
 	cd zlib/; \
 	$(CC) $(UCFLAGS) -c adler32.c crc32.c deflate.c inffast.c inflate.c inftrees.c trees.c zutil.c gzlib.c gzread.c; \
 	ar rcs ../libz.a adler32.o crc32.o deflate.o inffast.o inflate.o inftrees.o trees.o zutil.o gzlib.o gzread.o
-libpng:
-	cp pngusr.h libpng/pngusr.h
-	make -C libpng/ -f scripts/makefile.linux-opt CC="$(CC)" CFLAGS="$(UCFLAGS) -DPNG_USER_CONFIG -Wno-macro-redefined" libpng.a
 mozjpeg:
 	cd mozjpeg/; \
 	export CC="$(CC)"; \
diff --git a/src/optipng/CMakeLists.txt b/src/optipng/CMakeLists.txt
index 1037a20..3c751e9 100644
--- a/src/optipng/CMakeLists.txt
+++ b/src/optipng/CMakeLists.txt
@@ -16,16 +16,14 @@ add_library(optipng
 add_library(optipng::optipng ALIAS optipng)
 
 #make sure that we are using custom zlib and custom libpng options
-set(PNG_BUILD_ZLIB ON CACHE BOOL "use custom zlib within libpng" FORCE)
 set(ZLIB_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../zlib/ CACHE FILEPATH "custom zlib directory" FORCE)
 if(NOT WIN32)
 	add_compile_options(-Wno-macro-redefined)
 endif()
 add_compile_definitions(PNG_USER_CONFIG)
 
-add_subdirectory(../libpng libpng EXCLUDE_FROM_ALL)
 target_link_libraries(optipng
-	png_static)
+	png)
 
 # libpng generates some header files that we need to be able to include
 target_include_directories(optipng
diff --git a/src/optipng/image.h b/src/optipng/image.h
index c439f84..8255fa0 100755
--- a/src/optipng/image.h
+++ b/src/optipng/image.h
@@ -13,7 +13,7 @@
 #ifndef OPNGCORE_IMAGE_H
 #define OPNGCORE_IMAGE_H
 
-#include "../libpng/png.h"
+#include <png.h>
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/optipng/opngreduc/opngreduc.h b/src/optipng/opngreduc/opngreduc.h
index a7e6553..06ef956 100755
--- a/src/optipng/opngreduc/opngreduc.h
+++ b/src/optipng/opngreduc/opngreduc.h
@@ -13,7 +13,7 @@
 
 #include <stdbool.h>
 
-#include "../../libpng/png.h"
+#include <png.h>
 
 
 #ifdef __cplusplus
diff --git a/src/optipng/trans.h b/src/optipng/trans.h
index a2f7f3e..c0e8dc4 100755
--- a/src/optipng/trans.h
+++ b/src/optipng/trans.h
@@ -13,7 +13,7 @@
 #ifndef OPNGTRANS_TRANS_H
 #define OPNGTRANS_TRANS_H
 
-#include "../libpng/png.h"
+#include <png.h>
 
 #ifdef __cplusplus
 extern "C" {