diff --git a/docs/contributing/how-to-update-third-party-library.md b/docs/contributing/how-to-update-third-party-library.md
index 5c16d2114d..b5fb4dcbf0 100644
--- a/docs/contributing/how-to-update-third-party-library.md
+++ b/docs/contributing/how-to-update-third-party-library.md
@@ -142,5 +142,6 @@ Example updating libpng files under MSW:
 3) in libpng root dir run:
    mingw32-make png.lo
    (will generate pnglibconf.h and pngprefix.h, among others)
-4) copy files from libpng root dir and scripts subfolder to src/png, updating old files only (other new files were not needed);
-5) commit the changes.
+4) edit pnglibconf.h and change the value of PNG_ZLIB_VERNUM to 0.
+5) copy files from libpng root dir and scripts subfolder to src/png, updating old files only (other new files were not needed);
+6) commit the changes.
diff --git a/src/png/pnglibconf.h b/src/png/pnglibconf.h
index 4b330136ea..73b79e7319 100644
--- a/src/png/pnglibconf.h
+++ b/src/png/pnglibconf.h
@@ -204,7 +204,7 @@
 #define PNG_USER_HEIGHT_MAX 1000000
 #define PNG_USER_WIDTH_MAX 1000000
 #define PNG_ZBUF_SIZE 8192
-#define PNG_ZLIB_VERNUM 0x12a0
+#define PNG_ZLIB_VERNUM 0
 #define PNG_Z_DEFAULT_COMPRESSION (-1)
 #define PNG_Z_DEFAULT_NOFILTER_STRATEGY 0
 #define PNG_Z_DEFAULT_STRATEGY 1