diff --git a/builder/index.js b/builder/index.js
index 6d66183..94a446d 100644
--- a/builder/index.js
+++ b/builder/index.js
@@ -33,7 +33,7 @@ const fs = require("fs");
 const os = require("os");
 const path = require("path");
 const { MIME_TYPES, ALL_FILES } = require("./mime");
-const { installerScript, columnsOf, MAX_COLUMNS, ROWS } = require("./installer");
+const { installerScript, columnsOf, MAX_COLUMNS, ROWS, MAX_LABEL } = require("./installer");
 
 /** What an app's config extends: the kit's base config, by the package's name. */
 const KIT_BASE = "@diamonddigitaldev/electron-kit/builder/base.json";
@@ -89,6 +89,9 @@ function checkContextMenu(contextMenu) {
     if (typeof contextMenu.label !== "string" || contextMenu.label.trim() === "" || /["\r\n]/.test(contextMenu.label)) {
         throw new Error("config(): contextMenu.label must be the entry's text, such as \"Convert with App\", on one line, without quotes.");
     }
+    if (contextMenu.label.length > MAX_LABEL) {
+        throw new Error(`config(): contextMenu.label is ${contextMenu.label.length} characters; the installer's line holds ${MAX_LABEL}. Shorten it, such as "Convert with App".`);
+    }
     if (contextMenu.folders !== undefined && typeof contextMenu.folders !== "boolean") throw new Error("config(): contextMenu.folders must be true or false.");
     if (contextMenu.args !== undefined && (!Array.isArray(contextMenu.args) || !contextMenu.args.every((arg) => typeof arg === "string" && /^--[a-z0-9][a-z0-9-]*(=[A-Za-z0-9._-]+)?$/.test(arg)))) {
         throw new Error("config(): contextMenu.args must be switches, such as [\"--upload\"].");
diff --git a/builder/installer.js b/builder/installer.js
index 0c454cc..71784b2 100644
--- a/builder/installer.js
+++ b/builder/installer.js
@@ -32,6 +32,13 @@
 const MAX_COLUMNS = 4;
 const ROWS = 8;
 
+/**
+ * The longest right-click label the page's line holds: 'Add "<label>" to the
+ * right-click menu' wraps past about ninety characters, and a checkbox one line
+ * high shows the middle of two lines, clipped top and bottom.
+ */
+const MAX_LABEL = 48;
+
 /** A string inside NSIS's double quotes. */
 function nsisString(text) {
     return String(text)
@@ -169,9 +176,8 @@ function installerScript({ productName, description = "", fileTypes, contextMenu
         );
     }
     if (contextMenu) {
-        const where = contextMenu.folders ? "files and folders" : "files";
         lines.push(
-            `    \${NSD_CreateCheckbox} 0u ${exts.length > 0 ? 129 : 0}u 100% 10u "Add $\\"${controlText(contextMenu.label)}$\\" to the menu when you right-click ${where}"`,
+            `    \${NSD_CreateCheckbox} 0u ${exts.length > 0 ? 129 : 0}u 100% 10u "Add $\\"${controlText(contextMenu.label)}$\\" to the right-click menu"`,
             "    Pop $KitMenuBox",
             '    ${if} $KitMenu == "1"',
             "      ${NSD_Check} $KitMenuBox",
@@ -347,4 +353,4 @@ function installerScript({ productName, description = "", fileTypes, contextMenu
     return lines.join("\r\n") + "\r\n";
 }
 
-module.exports = { installerScript, columnsOf, nsisString, MAX_COLUMNS, ROWS };
+module.exports = { installerScript, columnsOf, nsisString, MAX_COLUMNS, ROWS, MAX_LABEL };
diff --git a/docs/building.md b/docs/building.md
index 6363de0..872f2b0 100644
--- a/docs/building.md
+++ b/docs/building.md
@@ -91,7 +91,8 @@ contextMenu: { label: "Convert with Diamond File Converter", folders: true },
 
 `contextMenu` is the app's entry on the menu Explorer shows when a file is right-clicked: its `label`,
 `folders: true` to show it on folders too, and `args`, switches given after the file (Dropgate's
-`["--upload"]`).
+`["--upload"]`). The installer's box for it reads `Add "<label>" to the right-click menu` on one line, so a
+`label` holds at most 48 characters.
 
 ### The Asking Installer (Windows)
 
diff --git a/test/builder.test.js b/test/builder.test.js
index 1d12da1..d6074c3 100644
--- a/test/builder.test.js
+++ b/test/builder.test.js
@@ -185,6 +185,7 @@ test("config() refuses what would claim types without asking, or leave the .desk
         [[PKG, { build: BUILD, contextMenu: "Convert" }], /contextMenu must be \{ label/],
         [[PKG, { build: BUILD, contextMenu: { label: "" } }], /contextMenu\.label must be/],
         [[PKG, { build: BUILD, contextMenu: { label: 'Open "it"' } }], /contextMenu\.label must be/],
+        [[PKG, { build: BUILD, contextMenu: { label: "Convert with ".padEnd(49, "x") } }], /contextMenu\.label is 49 characters; the installer's line holds 48/],
         [[PKG, { build: BUILD, contextMenu: { label: "Open", verb: "open" } }], /contextMenu\.verb isn't an option/],
         [[PKG, { build: BUILD, contextMenu: { label: "Open", folders: "yes" } }], /contextMenu\.folders must be/],
         [[PKG, { build: BUILD, contextMenu: { label: "Open", args: ["upload"] } }], /contextMenu\.args must be switches/],
@@ -229,7 +230,7 @@ test("the installer: a box per file type in its group's column, all ticked unles
         assert.ok(script.includes(`WriteRegStr SHELL_CONTEXT "\${INSTALL_REGISTRY_KEY}" "KitFileType.${ext}" "$KitType${i}"`), ext);
     });
     assert.match(script, /"Tick All"[\s\S]*"Untick All"/);
-    assert.match(script, /"Add \$\\"Convert with Diamond File Converter\$\\" to the menu when you right-click files and folders"/);
+    assert.match(script, /"Add \$\\"Convert with Diamond File Converter\$\\" to the right-click menu"/);
     assert.match(script, /\$\{GetOptions\} \$R0 "\/FILETYPES=" \$R1/);
     assert.match(script, /\$\{GetOptions\} \$R0 "\/NOCONTEXTMENU" \$R1/);
     // An update (--updated) never shows it.
@@ -276,7 +277,7 @@ test("the installer: an app that takes any file asks only about its right-click
     assert.doesNotMatch(script, /Choose File Types|KitListHas|KitType|FILETYPES|RegisteredApplications|Directory\\shell/);
     assert.match(script, /WriteRegStr SHELL_CONTEXT "Software\\Classes\\\*\\shell\\DropgateClient\\command" "" '"\$appExe" "%1" --upload'/);
     assert.match(script, /WriteRegStr SHELL_CONTEXT "Software\\Classes\\\*\\shell\\DropgateClient" "MultiSelectModel" "Player"/);
-    assert.match(script, /"Add \$\\"Share with Dropgate\$\\" to the menu when you right-click files"/);
+    assert.match(script, /"Add \$\\"Share with Dropgate\$\\" to the right-click menu"/);
 });
 
 test("the installer: text from the app is kept as text in NSIS's strings", () => {