Index: binaries/data/mods/public/gui/common/campaigns/CampaignRun.js
===================================================================
--- binaries/data/mods/public/gui/common/campaigns/CampaignRun.js
+++ binaries/data/mods/public/gui/common/campaigns/CampaignRun.js
@@ -2,6 +2,26 @@
 // TODO: Move this to a static member once linters accept it.
 var g_CurrentCampaignRun;
 
+class CampaignRunDoesNotExistError extends Error
+{
+	toString()
+	{
+		return sprintf(translate("Campaign file %(file)s does not exist."), {
+			"file": this.message
+		});
+	}
+};
+
+class CampaignTemplateCannotLoadError extends Error
+{
+	toString()
+	{
+		return sprintf(translate("Campaign template %(file)s does not exist (perhaps it comes from a mod?)."), {
+			"file": this.message
+		});
+	}
+}
+
 /**
  * A campaign "Run" saves metadata on a campaign progession.
  * It is equivalent to a saved game for a game.
@@ -122,13 +142,13 @@
 	load()
 	{
 		if (!Engine.FileExists("saves/campaigns/" + this.filename + ".0adcampaign"))
-			throw new Error("Campaign file does not exist");
+			throw new CampaignRunDoesNotExistError(this.filename);
 		let data = Engine.ReadJSONFile("saves/campaigns/" + this.filename + ".0adcampaign");
 		this.data = data.data;
 		this.meta = data.meta;
 		this.template = CampaignTemplate.getTemplate(data.template_identifier);
 		if (!this.template)
-			throw new Error("Campaign template " + data.template_identifier + " does not exist (perhaps it comes from a mod?)");
+			throw new CampaignTemplateCannotLoadError(data.template_identifier);
 		return this;
 	}