diff --git a/classes/external/get_dependingmodules.php b/classes/external/get_dependingmodules.php
index 4ec0d28..060e928 100644
--- a/classes/external/get_dependingmodules.php
+++ b/classes/external/get_dependingmodules.php
@@ -89,7 +89,7 @@ public static function execute_returns(): external_single_structure {
     public static function execute(int $cmid): array {
         $params = self::validate_parameters(self::execute_parameters(), ['cmId' => $cmid]);
         $cmid = $params['cmId'];
-        [$course, $cminfo] = get_course_and_cm_from_cmid($cmid);
+        [$course, $cminfo] = get_course_and_cm_from_cmid($cmid, 'learningmap');
         $context = context_module::instance($cmid);
         self::validate_context($context);
         require_capability('mod/learningmap:view', $context);
diff --git a/classes/external/get_learningmap.php b/classes/external/get_learningmap.php
index 68caf94..be0b81d 100644
--- a/classes/external/get_learningmap.php
+++ b/classes/external/get_learningmap.php
@@ -90,7 +90,7 @@ public static function execute(int $cmid): array {
         global $PAGE, $OUTPUT;
         $params = self::validate_parameters(self::execute_parameters(), ['cmId' => $cmid]);
         $cmid = $params['cmId'];
-        [$course, $cminfo] = get_course_and_cm_from_cmid($cmid);
+        [$course, $cminfo] = get_course_and_cm_from_cmid($cmid, 'learningmap');
         $context = context_module::instance($cmid);
         // Don't render learningmap if not available and user has no override capability.
         if (!$cminfo->available && !has_capability('moodle/course:ignoreavailabilityrestrictions', $context)) {
diff --git a/tests/external/external_test.php b/tests/external/external_test.php
new file mode 100644
index 0000000..6a439e1
--- /dev/null
+++ b/tests/external/external_test.php
@@ -0,0 +1,69 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+namespace mod_learningmap\external;
+
+/**
+ * Tests for the web service functions of mod_learningmap.
+ *
+ * @package    mod_learningmap
+ * @copyright  2026 ISB Bayern
+ * @author     Dr. Peter Mayer
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+final class external_test extends \advanced_testcase {
+    #[\PHPUnit\Framework\Attributes\RunInSeparateProcess]
+    /**
+     * The web services only accept course modules of type learningmap.
+     *
+     * @covers \mod_learningmap\external\get_learningmap::execute
+     * @covers \mod_learningmap\external\get_dependingmodules::execute
+     * @runInSeparateProcess
+     */
+    public function test_execute_rejects_other_module_types(): void {
+        global $CFG, $DB;
+        $this->resetAfterTest();
+        $generator = $this->getDataGenerator();
+        $course = $generator->create_course();
+        $student = $generator->create_and_enrol($course, 'student');
+        $page = $generator->create_module('page', ['course' => $course->id]);
+        // The own map needs no places, its rendering is not under test.
+        $placestore = json_decode(file_get_contents($CFG->dirroot . '/mod/learningmap/tests/generator/test.json'), true);
+        $placestore = array_merge($placestore, ['places' => [], 'paths' => [], 'startingplaces' => [], 'targetplaces' => []]);
+        $ownmap = $generator->create_module('learningmap', ['course' => $course->id, 'placestore' => json_encode($placestore)]);
+
+        // A map in a foreign course whose instance id equals the id of the page.
+        $othercourse = $generator->create_course();
+        $othermap = $generator->create_module('learningmap', ['course' => $othercourse->id]);
+        $DB->set_field('learningmap', 'id', $page->id, ['id' => $othermap->id]);
+        $DB->set_field('course_modules', 'instance', $page->id, ['id' => $othermap->cmid]);
+        rebuild_course_cache($othercourse->id, true);
+
+        $this->setUser($student);
+        $functions = [get_learningmap::class, get_dependingmodules::class];
+        foreach ($functions as $function) {
+            try {
+                $function::execute($page->cmid);
+                $this->fail('Expected moodle_exception for ' . $function);
+            } catch (\moodle_exception $e) {
+                $this->assertSame('invalidcoursemoduleid', $e->errorcode);
+            }
+        }
+
+        $this->assertNotEmpty(get_learningmap::execute($ownmap->cmid)['content']);
+        $this->assertIsArray(get_dependingmodules::execute($ownmap->cmid));
+    }
+}
diff --git a/tests/mod_learningmap_helper_test.php b/tests/mod_learningmap_helper_test.php
index bb7108f..703b883 100644
--- a/tests/mod_learningmap_helper_test.php
+++ b/tests/mod_learningmap_helper_test.php
@@ -16,6 +16,9 @@
 
 namespace mod_learningmap;
 
+#[\PHPUnit\Framework\Attributes\CoversClass(helper::class)]
+#[\PHPUnit\Framework\Attributes\CoversMethod(helper::class, 'repair_learningmap_record')]
+#[\PHPUnit\Framework\Attributes\CoversMethod(helper::class, 'render_activity_header_for_modal')]
 /**
  * Tests for Learning map helper class
  *
@@ -23,10 +26,8 @@
  * @category   test
  * @copyright  2025 ISB Bayern
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ * @covers     \mod_learningmap\helper
  */
-#[\PHPUnit\Framework\Attributes\CoversClass(helper::class)]
-#[\PHPUnit\Framework\Attributes\CoversMethod(helper::class, 'repair_learningmap_record')]
-#[\PHPUnit\Framework\Attributes\CoversMethod(helper::class, 'render_activity_header_for_modal')]
 final class mod_learningmap_helper_test extends \advanced_testcase {
     /**
      * Tests the repair_learningmap_record method.