diff --git a/keydb_extension.go b/keydb_extension.go
index af473b8..4b31605 100644
--- a/keydb_extension.go
+++ b/keydb_extension.go
@@ -76,9 +76,15 @@ func (h *KeyDBHandler) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 					return d.ArgErr()
 				}
 			case "db":
-				if !d.Args(strconv.Atoi(&h.DB)) {
+				var dbStr string
+				if !d.Args(&dbStr) {
 					return d.ArgErr()
 				}
+				db, err := strconv.Atoi(dbStr)
+				if err != nil {
+					return d.Errf("invalid db number: %v", err)
+				}
+				h.DB = db
 			}
 		}
 	}