diff --git a/system/HTTP/SiteURI.php b/system/HTTP/SiteURI.php
index 84488a307bca..9f5cbb56ba5a 100644
--- a/system/HTTP/SiteURI.php
+++ b/system/HTTP/SiteURI.php
@@ -180,6 +180,14 @@ private function setBasePath(string $baseURL): void
         }
     }
 
+    /**
+     * @deprecated
+     */
+    public function setBaseURL(string $baseURL): void
+    {
+        throw new BadMethodCallException('Cannot use this method.');
+    }
+
     /**
      * @deprecated
      */
diff --git a/tests/system/HTTP/SiteURITest.php b/tests/system/HTTP/SiteURITest.php
index 9a8caa3a7d95..578074ef5d6f 100644
--- a/tests/system/HTTP/SiteURITest.php
+++ b/tests/system/HTTP/SiteURITest.php
@@ -336,6 +336,16 @@ public function testSetURI()
         $uri->setURI('http://another.site.example.jp/');
     }
 
+    public function testSetBaseURI()
+    {
+        $this->expectException(BadMethodCallException::class);
+
+        $config = new App();
+        $uri    = new SiteURI($config);
+
+        $uri->setBaseURL('http://another.site.example.jp/');
+    }
+
     public function testGetBaseURL()
     {
         $config = new App();