diff --git a/remote/.eslintrc.js b/remote/.eslintrc.js
index 1ba4a03c8ee0..f386a7357602 100644
--- a/remote/.eslintrc.js
+++ b/remote/.eslintrc.js
@@ -3,5 +3,6 @@
 module.exports = {
   "rules": {
     "max-len": "off",
+    "no-tabs": "off",
   }
 };
diff --git a/remote/Error.jsm b/remote/Error.jsm
index abd832627a46..77b41ed66d12 100644
--- a/remote/Error.jsm
+++ b/remote/Error.jsm
@@ -71,18 +71,25 @@ class UnsupportedError extends RemoteAgentError {}
 class UnknownMethodError extends RemoteAgentError {}
 
 function formatError(error, {stack = false} = {}) {
-  const ls = [];
+  const els = [];
 
-  ls.push(`${error.name}: ${error.message ? `${error.message}:` : ""}`);
+  els.push(error.name);
+  if (error.message) {
+    els.push(": ");
+    els.push(error.message);
+  }
 
   if (stack && error.stack) {
+    els.push(":\n");
+
     const stack = error.stack.trim().split("\n");
-    ls.push(stack.map(line => `\t${line}`).join("\n"));
+    els.push(stack.map(line => `\t${line}`).join("\n"));
 
     if (error.cause) {
-      ls.push("caused by: " + formatError(error.cause, {stack}));
+      els.push("\n");
+      els.push("caused by: " + formatError(error.cause, {stack}));
     }
   }
 
-  return ls.join("\n");
+  return els.join("");
 }
diff --git a/remote/test/unit/test_Error.js b/remote/test/unit/test_Error.js
index 279a579e0f33..e5d760969761 100644
--- a/remote/test/unit/test_Error.js
+++ b/remote/test/unit/test_Error.js
@@ -46,15 +46,15 @@ add_test(function test_RemoteAgentError_toString() {
 add_test(function test_RemoteAgentError_format() {
   const {format} = RemoteAgentError;
 
-  equal(format({name: "HippoError"}), "HippoError: ");
-  equal(format({name: "HorseError", message: "neigh"}), "HorseError: neigh:");
+  equal(format({name: "HippoError"}), "HippoError");
+  equal(format({name: "HorseError", message: "neigh"}), "HorseError: neigh");
 
   const dog = {
     name: "DogError",
     message: "woof",
     stack: "  one\ntwo\nthree  ",
   };
-  equal(format(dog), "DogError: woof:");
+  equal(format(dog), "DogError: woof");
   equal(format(dog, {stack: true}),
 `DogError: woof:
 	one
@@ -67,7 +67,7 @@ add_test(function test_RemoteAgentError_format() {
     stack: "four\nfive\nsix",
     cause: dog,
   };
-  equal(format(cat), "CatError: meow:");
+  equal(format(cat), "CatError: meow");
   equal(format(cat, {stack: true}),
 `CatError: meow:
 	four