diff --git a/web/app.js b/web/app.js
index 3c5e80856..02436ff4a 100644
--- a/web/app.js
+++ b/web/app.js
@@ -1004,16 +1004,6 @@ const PDFViewerApplication = {
       AppOptions.set("docBaseUrl", this.baseUrl);
     }
 
-    // On Android, there is almost no chance to have the font we want so we
-    // don't use the system fonts in this case.
-    if (
-      typeof PDFJSDev === "undefined"
-        ? window.isGECKOVIEW
-        : PDFJSDev.test("GECKOVIEW")
-    ) {
-      args.useSystemFonts = false;
-    }
-
     // Set the necessary API parameters, using all the available options.
     const apiParams = AppOptions.getAll(OptionKind.API);
     const loadingTask = getDocument({
diff --git a/web/app_options.js b/web/app_options.js
index acb18e434..7940d9786 100644
--- a/web/app_options.js
+++ b/web/app_options.js
@@ -39,6 +39,14 @@ if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
       compatParams.set("maxCanvasPixels", 5242880);
     }
   })();
+
+  // Don't use system fonts on Android (issue 18210).
+  // Support: Android
+  (function () {
+    if (isAndroid) {
+      compatParams.set("useSystemFonts", false);
+    }
+  })();
 }
 
 const OptionKind = {
@@ -47,6 +55,7 @@ const OptionKind = {
   API: 0x04,
   WORKER: 0x08,
   EVENT_DISPATCH: 0x10,
+  UNDEF_ALLOWED: 0x20,
   PREFERENCE: 0x80,
 };
 
@@ -385,6 +394,19 @@ const defaultOptions = {
           : "../web/standard_fonts/",
     kind: OptionKind.API,
   },
+  useSystemFonts: {
+    // On Android, there is almost no chance to have the font we want so we
+    // don't use the system fonts in this case (bug 1882613).
+    /** @type {boolean|undefined} */
+    value: (
+      typeof PDFJSDev === "undefined"
+        ? window.isGECKOVIEW
+        : PDFJSDev.test("GECKOVIEW")
+    )
+      ? false
+      : undefined,
+    kind: OptionKind.API + OptionKind.UNDEF_ALLOWED,
+  },
   verbosity: {
     /** @type {number} */
     value: 1,
@@ -472,6 +494,11 @@ if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING || LIB")) {
       if (kind & OptionKind.BROWSER) {
         throw new Error(`Cannot mix "PREFERENCE" and "BROWSER" kind: ${name}`);
       }
+      if (kind & OptionKind.UNDEF_ALLOWED) {
+        throw new Error(
+          `Cannot allow \`undefined\` value for "PREFERENCE" kind: ${name}`
+        );
+      }
       if (typeof compatParams === "object" && compatParams.has(name)) {
         throw new Error(
           `Should not have compatibility-value for "PREFERENCE" kind: ${name}`
@@ -486,6 +513,11 @@ if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING || LIB")) {
         throw new Error(`Invalid value for "PREFERENCE" kind: ${name}`);
       }
     } else if (kind & OptionKind.BROWSER) {
+      if (kind & OptionKind.UNDEF_ALLOWED) {
+        throw new Error(
+          `Cannot allow \`undefined\` value for "BROWSER" kind: ${name}`
+        );
+      }
       if (typeof compatParams === "object" && compatParams.has(name)) {
         throw new Error(
           `Should not have compatibility-value for "BROWSER" kind: ${name}`
@@ -514,23 +546,30 @@ class AppOptions {
   static getAll(kind = null, defaultOnly = false) {
     const options = Object.create(null);
     for (const name in defaultOptions) {
-      const defaultOption = defaultOptions[name];
+      const defaultOpt = defaultOptions[name];
 
-      if (kind && !(kind & defaultOption.kind)) {
+      if (kind && !(kind & defaultOpt.kind)) {
         continue;
       }
       options[name] =
         !defaultOnly && userOptions.has(name)
           ? userOptions.get(name)
-          : defaultOption.value;
+          : defaultOpt.value;
     }
     return options;
   }
 
   static set(name, value) {
-    const defaultOption = defaultOptions[name];
+    const defaultOpt = defaultOptions[name];
 
-    if (!defaultOption || typeof value !== typeof defaultOption.value) {
+    if (
+      !defaultOpt ||
+      !(
+        typeof value === typeof defaultOpt.value ||
+        (defaultOpt.kind & OptionKind.UNDEF_ALLOWED &&
+          (value === undefined || defaultOpt.value === undefined))
+      )
+    ) {
       return;
     }
     userOptions.set(name, value);
@@ -540,23 +579,30 @@ class AppOptions {
     let events;
 
     for (const name in options) {
-      const defaultOption = defaultOptions[name],
-        userOption = options[name];
+      const defaultOpt = defaultOptions[name],
+        userOpt = options[name];
 
-      if (!defaultOption || typeof userOption !== typeof defaultOption.value) {
+      if (
+        !defaultOpt ||
+        !(
+          typeof userOpt === typeof defaultOpt.value ||
+          (defaultOpt.kind & OptionKind.UNDEF_ALLOWED &&
+            (userOpt === undefined || defaultOpt.value === undefined))
+        )
+      ) {
         continue;
       }
       if (prefs) {
-        const { kind } = defaultOption;
+        const { kind } = defaultOpt;
 
         if (!(kind & OptionKind.BROWSER || kind & OptionKind.PREFERENCE)) {
           continue;
         }
         if (this.eventBus && kind & OptionKind.EVENT_DISPATCH) {
-          (events ||= new Map()).set(name, userOption);
+          (events ||= new Map()).set(name, userOpt);
         }
       }
-      userOptions.set(name, userOption);
+      userOptions.set(name, userOpt);
     }
 
     if (events) {
diff --git a/web/viewer-geckoview.html b/web/viewer-geckoview.html
index 7d0d936f7..dee94a04d 100644
--- a/web/viewer-geckoview.html
+++ b/web/viewer-geckoview.html
@@ -42,6 +42,12 @@ See https://github.com/adobe-type-tools/cmap-resources
 <!--#endif-->
 
 <!--#if !MOZCENTRAL-->
+    <script>
+      if (typeof PDFJSDev === "undefined") {
+        window.isGECKOVIEW = true;
+      }
+    </script>
+
     <script type="importmap">
       {
         "imports": {
diff --git a/web/viewer-geckoview.js b/web/viewer-geckoview.js
index 962eddd76..2b9fd1ace 100644
--- a/web/viewer-geckoview.js
+++ b/web/viewer-geckoview.js
@@ -60,9 +60,6 @@ function getViewerConfiguration() {
 function webViewerLoad() {
   const config = getViewerConfiguration();
 
-  if (typeof PDFJSDev === "undefined") {
-    window.isGECKOVIEW = true;
-  }
   PDFViewerApplication.run(config);
 }