--- a/browser/components/enterprisepolicies/PoliciesValidator.jsm
+++ b/browser/components/enterprisepolicies/PoliciesValidator.jsm
@@ -47,16 +47,24 @@ function validateAndParseParamRecursive(
     case "number":
     case "integer":
     case "string":
     case "URL":
     case "origin":
       return validateAndParseSimpleParam(param, properties.type);
 
     case "array":
+      if (param === undefined) {
+        // Accept a missing array as valid. Policies that use
+        // arrays should still check before iterating through
+        // the array, unless it is marked as "required" in the
+        // schema (but "required" is not implemented yet).
+        return [true, undefined];
+      }
+
       if (!Array.isArray(param)) {
         log.error("Array expected but not received");
         return [false, null];
       }
 
       let parsedArray = [];
       for (let item of param) {
         log.debug(`in array, checking @${item}@ for type ${properties.items.type}`);

--- a/browser/components/enterprisepolicies/tests/browser/browser_policies_validate_and_parse_API.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policies_validate_and_parse_API.js
@@ -223,8 +223,39 @@ add_task(async function test_array_of_ob
   ok(typeof(parsed[0]) == "object" && typeof(parsed[1]) == "object", "Correct objects inside array");
 
   is(parsed[0].url.spec, "https://www.example.com/bookmark1", "Correct URL for bookmark 1");
   is(parsed[1].url.spec, "https://www.example.com/bookmark2", "Correct URL for bookmark 2");
 
   is(parsed[0].title, "Foo", "Correct title for bookmark 1");
   is(parsed[1].title, "Bar", "Correct title for bookmark 2");
 });
+
+add_task(async function test_missing_arrays_inside_objects() {
+  let schema = {
+    type: "object",
+    properties: {
+      allow: {
+        type: "array",
+        items: {
+          type: "boolean"
+        }
+      },
+      block: {
+        type: "array",
+        items: {
+          type: "boolean"
+        }
+      }
+
+    }
+  };
+
+  let valid, parsed;
+  [valid, parsed] = PoliciesValidator.validateAndParseParameters({
+    allow: [true, true, true]
+  }, schema);
+
+  ok(valid, "Object is valid");
+  is(parsed.allow.length, 3, "Allow array is correct.");
+  is(parsed.block, undefined, "Block array is undefined, as expected.");
+});
+