diff --git a/ext/libpng17/CMakeLists.txt b/ext/libpng17/CMakeLists.txt
index 7d6ae56ccb..6c155a686a 100644
--- a/ext/libpng17/CMakeLists.txt
+++ b/ext/libpng17/CMakeLists.txt
@@ -19,6 +19,7 @@ add_library(png17 STATIC
 	pngrutil.c
 	pngset.c
 	pngstruct.h
+	pngtest.c
 	pngtrans.c
 	pngwio.c
 	pngwrite.c