diff --git a/src/functions.php b/src/functions.php
index cdb5ab2..6f80676 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -2,25 +2,27 @@
 
 namespace LibDNS;
 
-if (\function_exists('idn_to_ascii')) {
-    function normalize_name(string $label): string
-    {
-        if (false === $result = \idn_to_ascii($label, 0, INTL_IDNA_VARIANT_UTS46)) {
-            throw new \InvalidArgumentException("Label '{$label}' could not be processed for IDN");
-        }
+if (!\function_exists('LibDNS\\normalize_name')) {
+    if (\function_exists('idn_to_ascii')) {
+        function normalize_name(string $label): string
+        {
+            if (false === $result = \idn_to_ascii($label, 0, INTL_IDNA_VARIANT_UTS46)) {
+                throw new \InvalidArgumentException("Label '{$label}' could not be processed for IDN");
+            }
 
-        return $result;
-    }
-} else {
-    function normalize_name(string $label): string
-    {
-        if (\preg_match('/[\x80-\xff]/', $label)) {
-            throw new \InvalidArgumentException(
-                "Label '{$label}' contains non-ASCII characters and IDN support is not available."
-                . " Verify that ext/intl is installed for IDN support."
-            );
+            return $result;
         }
+    } else {
+        function normalize_name(string $label): string
+        {
+            if (\preg_match('/[\x80-\xff]/', $label)) {
+                throw new \InvalidArgumentException(
+                    "Label '{$label}' contains non-ASCII characters and IDN support is not available."
+                    ." Verify that ext/intl is installed for IDN support."
+                );
+            }
 
-        return \strtolower($label);
+            return \strtolower($label);
+        }
     }
 }