diff --git a/src/standard.c b/src/standard.c
index f57724c..9299882 100644
--- a/src/standard.c
+++ b/src/standard.c
@@ -709,6 +709,11 @@
 		goto out;
 	}
 
+	if (!*str2) {
+		memprintf(err, "'%s' resolves to an empty address (environment variable missing?)\n", str);
+		goto out;
+	}
+
 	memset(&ss, 0, sizeof(ss));
 
 	if (strncmp(str2, "unix@", 5) == 0) {