diff --git a/configure.ac b/configure.ac
index add3a5bc..5e3c7f01 100644
--- a/configure.ac
+++ b/configure.ac
@@ -107,6 +107,7 @@ fi
 
 NEED_PROG(curl, curl)
 NEED_PROG(shell, sh)
+NEED_PROG(patch, patch)
 AC_PATH_PROG(xmllint, xmllint, false)
 AC_PATH_PROG(xsltproc, xsltproc, false)
 AC_PATH_PROG(jing, jing, false) # needed because xmllint --relaxng seems broken
diff --git a/externals/Makefile.am b/externals/Makefile.am
index 07258aab..75984fce 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)
@@ -46,7 +46,7 @@ $(ATERM).tar.gz:
 
 $(ATERM): $(ATERM).tar.gz
 	gunzip < $(srcdir)/$(ATERM).tar.gz | tar xvf -
-	(cd $(ATERM) && patch -p1) < $(srcdir)/aterm-aliasing.patch
+	(cd $(ATERM) && $(patch) -p1) < $(srcdir)/aterm-aliasing.patch
 
 have-aterm:
 	$(MAKE) $(ATERM)