diff --git a/GNUmakefile.in b/GNUmakefile.in
index 2352fc1171a..cb613086c7c 100644
--- a/GNUmakefile.in
+++ b/GNUmakefile.in
@@ -68,10 +68,10 @@ check check-tests installcheck installcheck-parallel installcheck-tests: CHECKPR
 check check-tests installcheck installcheck-parallel installcheck-tests: submake-generated-headers
 	$(MAKE) -C src/test/regress $@
 
-$(call recurse,check-world,src/test src/pl src/interfaces/ecpg contrib src/bin,check)
-$(call recurse,checkprep,  src/test src/pl src/interfaces/ecpg contrib src/bin)
+$(call recurse,check-world,src/test src/pl src/interfaces/ecpg src/interfaces/libpq contrib src/bin,check)
+$(call recurse,checkprep,  src/test src/pl src/interfaces/ecpg src/interfaces/libpq contrib src/bin)
 
-$(call recurse,installcheck-world,src/test src/pl src/interfaces/ecpg contrib src/bin,installcheck)
+$(call recurse,installcheck-world,src/test src/pl src/interfaces/ecpg src/interfaces/libpq contrib src/bin,installcheck)
 $(call recurse,install-tests,src/test/regress,install-tests)
 
 GNUmakefile: GNUmakefile.in $(top_builddir)/config.status