diff --git a/Makefile.am b/Makefile.am
index e22abfa5718fe77caef7278d4420aeafebed3efe..b128541f7da9f7d50c983a033ec893de64c8ade5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -171,6 +171,9 @@ $(top_srcdir)/configure.ac: force
 	    dist-* | dist | distcheck | distclean) _arg=release ;; \
 	esac; \
 	if ! $(top_srcdir)/update_version $$_arg 2> /dev/null; then \
+	    if [ ! -e $(top_srcdir)/package_version ]; then \
+		echo 'PACKAGE_VERSION="unknown"' > $(top_srcdir)/package_version; \
+	    fi; \
 	    . $(top_srcdir)/package_version || exit 1; \
 	    [ "$(PACKAGE_VERSION)" != "$$PACKAGE_VERSION" ] || exit 0; \
 	fi; \
diff --git a/Makefile.unix b/Makefile.unix
index 84244bf77a622df899202f1bcc7a120d9126278a..7d37995d56fbf73528b5efc6203d92285b97868a 100644
--- a/Makefile.unix
+++ b/Makefile.unix
@@ -116,7 +116,11 @@ celt/celt.o: CFLAGS += -DPACKAGE_VERSION='$(PACKAGE_VERSION)'
 celt/celt.o: package_version
 
 package_version: force
-	@./update_version || true
+	@if [ -x ./update_version ]; then \
+		./update_version || true; \
+	elif [ ! -e ./package_version ]; then \
+		echo 'PACKAGE_VERSION="unknown"' > ./package_version; \
+	fi
 
 force: