diff --git a/src/Symfony/Component/String/Resources/functions.php b/src/Symfony/Component/String/Resources/functions.php
index a60e2ce08c..c950894f39 100644
--- a/src/Symfony/Component/String/Resources/functions.php
+++ b/src/Symfony/Component/String/Resources/functions.php
@@ -11,22 +11,28 @@
 
 namespace Symfony\Component\String;
 
-function u(?string $string = ''): UnicodeString
-{
-    return new UnicodeString($string ?? '');
+if (!\function_exists(u::class)) {
+    function u(?string $string = ''): UnicodeString
+    {
+        return new UnicodeString($string ?? '');
+    }
 }
 
-function b(?string $string = ''): ByteString
-{
-    return new ByteString($string ?? '');
+if (!\function_exists(b::class)) {
+    function b(?string $string = ''): ByteString
+    {
+        return new ByteString($string ?? '');
+    }
 }
 
-/**
- * @return UnicodeString|ByteString
- */
-function s(?string $string = ''): AbstractString
-{
-    $string = $string ?? '';
+if (!\function_exists(s::class)) {
+    /**
+     * @return UnicodeString|ByteString
+     */
+    function s(?string $string = ''): AbstractString
+    {
+        $string = $string ?? '';
 
-    return preg_match('//u', $string) ? new UnicodeString($string) : new ByteString($string);
+        return preg_match('//u', $string) ? new UnicodeString($string) : new ByteString($string);
+    }
 }
diff --git a/src/Symfony/Component/Translation/Resources/functions.php b/src/Symfony/Component/Translation/Resources/functions.php
index 7ce806b7d1..901d2f87ef 100644
--- a/src/Symfony/Component/Translation/Resources/functions.php
+++ b/src/Symfony/Component/Translation/Resources/functions.php
@@ -11,10 +11,12 @@
 
 namespace Symfony\Component\Translation;
 
-/**
- * @author Nate Wiebe <nate@northern.co>
- */
-function t(string $message, array $parameters = [], string $domain = null): TranslatableMessage
-{
-    return new TranslatableMessage($message, $parameters, $domain);
+if (!\function_exists(t::class)) {
+    /**
+     * @author Nate Wiebe <nate@northern.co>
+     */
+    function t(string $message, array $parameters = [], string $domain = null): TranslatableMessage
+    {
+        return new TranslatableMessage($message, $parameters, $domain);
+    }
 }