diff --git a/externals/Makefile.am b/externals/Makefile.am
index 467fd9e8f2..55c09bd78f 100644
--- a/externals/Makefile.am
+++ b/externals/Makefile.am
@@ -11,7 +11,7 @@ $(DB).tar.gz:
 
 $(DB): $(DB).tar.gz
 	gunzip < $(srcdir)/$(DB).tar.gz | tar xvf -
-	cd $(DB) && patch -p1 < $(srcdir)/bdb-cygwin.patch
+	(cd $(DB) && patch -p1) < $(srcdir)/bdb-cygwin.patch
 
 have-db:
 	$(MAKE) $(DB)