diff --git a/lib/tests/textlib_test.php b/lib/tests/textlib_test.php
index 6ffcf06ff9e..d9daf1a714b 100644
--- a/lib/tests/textlib_test.php
+++ b/lib/tests/textlib_test.php
@@ -91,6 +91,10 @@ class core_textlib_testcase extends advanced_testcase {
         $this->assertSame(textlib::convert($utf8, 'utf-8', 'GB18030'), $str);
         $this->assertSame(textlib::convert($str, 'GB18030', 'utf-8'), $utf8);
         $this->assertSame(textlib::convert($utf8, 'utf-8', 'utf-8'), $utf8);
+
+        $utf8 = "Žluťoučký koníček";
+        $this->assertSame('Zlutouck\'y kon\'icek', core_text::convert($utf8, 'utf-8', 'ascii'));
+        $this->assertSame($utf8, core_text::convert($utf8.chr(130), 'utf-8', 'utf-8'));
     }
 
     /**
diff --git a/lib/textlib.class.php b/lib/textlib.class.php
index 37351e0ca0e..4fe83afb500 100644
--- a/lib/textlib.class.php
+++ b/lib/textlib.class.php
@@ -178,11 +178,16 @@ class textlib {
             return '';
         }
 
-        if ($toCS === 'utf-8' and $fromCS === 'utf-8') {
-            return fix_utf8($text);
+        if ($fromCS === 'utf-8') {
+            $text = fix_utf8($text);
+            if ($toCS === 'utf-8') {
+                return $text;
+            }
         }
 
-        $result = iconv($fromCS, $toCS.'//TRANSLIT', $text);
+        // Prevent any error notices, do not use //IGNORE so that we get
+        // consistent result from Typo3 if iconv fails.
+        $result = @iconv($fromCS, $toCS.'//TRANSLIT', $text);
 
         if ($result === false or $result === '') {
             // note: iconv is prone to return empty string when invalid char encountered, or false if encoding unsupported