diff --git a/config.m4 b/config.m4
index d084808..8c91a53 100644
--- a/config.m4
+++ b/config.m4
@@ -14,6 +14,7 @@ PHP_REQUIRE_CXX()
 PHP_ADD_LIBRARY(stdc++, 1, PDLIB_SHARED_LIBADD)
 PHP_ADD_LIBRARY(openblas, 1, PDLIB_SHARED_LIBADD)
 PHP_ADD_LIBRARY(lapack, 1, PDLIB_SHARED_LIBADD)
+PHP_ADD_LIBRARY(png, 1, PDLIB_SHARED_LIBADD)
 PHP_SUBST(PDLIB_SHARED_LIBADD)
 
 PHP_ADD_INCLUDE(PHP_EXT_SRCDIR()/dlib)
@@ -30,7 +31,7 @@ src/vector.cc"
 dnl using C++11
 CXXFLAGS="-g -O3 -march=native"
 
-PHP_NEW_EXTENSION(pdlib, $pdlib_src_files, $ext_shared,, -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1 -DDLIB_NO_GUI_SUPPORT=1 -DDLIB_USE_BLAS -DDLIB_USE_LAPACK, cxx)
+PHP_NEW_EXTENSION(pdlib, $pdlib_src_files, $ext_shared,, -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1 -DDLIB_NO_GUI_SUPPORT=1 -DDLIB_USE_BLAS -DDLIB_USE_LAPACK -DDLIB_PNG_SUPPORT, cxx)
 
 AC_CONFIG_COMMANDS_POST([
   echo ""