diff --git a/client/allocrunner/taskrunner/envoy_bootstrap_hook.go b/client/allocrunner/taskrunner/envoy_bootstrap_hook.go
index 3aaf2d2e0..41f604500 100644
--- a/client/allocrunner/taskrunner/envoy_bootstrap_hook.go
+++ b/client/allocrunner/taskrunner/envoy_bootstrap_hook.go
@@ -381,7 +381,7 @@ func buildEnvoyBind(alloc *structs.Allocation, ifce, service, task string, taskE
 			}
 		}
 	}
-	return fmt.Sprintf("%s:%d", ifce, port)
+	return net.JoinHostPort(ifce, strconv.Itoa(port))
 }
 
 func (h *envoyBootstrapHook) writeConfig(filename, config string) error {