diff --git a/Makefile.am b/Makefile.am
index 500049a0f..8fe2eeb73 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -132,7 +132,7 @@ $(srcdir)/scripts/pnglibconf.h.prebuilt:
 # The following is necessary to ensure that the local pnglibconf.h is used, not
 # an installed one (this can happen immediately after on a clean system if
 # 'make test' is the first thing the user does.)
-pngvalid.o pngtest.o: pnglibconf.h
+contrib/libtests/pngvalid.o pngtest.o: pnglibconf.h
 
 # We must use -DPNG_NO_USE_READ_MACROS here even when the library may actually
 # be built with PNG_USE_READ_MACROS; this prevents the read macros from