diff --git a/docs/environment-variables.md b/docs/environment-variables.md
index de993fe..7fcc007 100644
--- a/docs/environment-variables.md
+++ b/docs/environment-variables.md
@@ -10,6 +10,7 @@
   - [`RAINBOW_GC_THRESHOLD`](#rainbow_gc_threshold)
   - [`RAINBOW_IPNS_MAX_CACHE_TTL`](#rainbow_ipns_max_cache_ttl)
   - [`RAINBOW_PEERING`](#rainbow_peering)
+  - [`RAINBOW_PEERING_SHARED_CACHE`](#rainbow_peering_shared_cache)
 - [Logging](#logging)
   - [`GOLOG_LOG_LEVEL`](#golog_log_level)
   - [`GOLOG_LOG_FMT`](#golog_log_fmt)
diff --git a/main.go b/main.go
index 2865511..43318d6 100644
--- a/main.go
+++ b/main.go
@@ -308,6 +308,8 @@ share the same seed as long as the indexes are different.
 				if err != nil {
 					return err
 				}
+			} else if rainbowSeedRegex.MatchString(maStr) {
+				return fmt.Errorf("unable to peer with %q without defining --seed-index of this instance first", maStr)
 			}
 
 			ai, err := peer.AddrInfoFromString(maStr)