diff --git a/Makefile b/Makefile
index 658c331..7a3cd5b 100644
--- a/Makefile
+++ b/Makefile
@@ -28,12 +28,12 @@ rpms: rpms-vm
 
 rpms-vm:
 	[ "$$BACKEND_VMM" != "" ] || { echo "error: you must define variable BACKEND_VMM" >&2 ; exit 1 ; }
-	lsb_release >/dev/null 2>&1 || { echo "error: you need lsb_release installed" >&2 ; exit 1 ; }
+	lsb_release >/dev/null 2>&1 || { echo "error: you need lsb_release (package lsb) installed" >&2 ; exit 1 ; }
 	type pandoc >/dev/null 2>&1 || { echo "error: you need pandoc installed" >&2 ; exit 1 ; }
 	type rpmsign >/dev/null 2>&1 || { echo "error: you need rpm-sign installed" >&2 ; exit 1 ; }
 	rpmbuild --define "_rpmdir $(RPMS_DIR)" -bb rpm_spec/core-vm.spec
 	rpmbuild --define "_rpmdir $(RPMS_DIR)" -bb rpm_spec/core-vm-doc.spec
-	[ "$$SKIP_SIGNING" = "" ] || rpm --addsign \
+	[ "$$SKIP_SIGNING" != "" ] || rpm --addsign \
 		$(RPMS_DIR)/x86_64/qubes-core-vm-*$(VERSION)*.rpm \
 		$(RPMS_DIR)/x86_64/qubes-core-vm-doc-*$(VERSION)*.rpm