diff --git a/src/CryptoEncoding/PEM.php b/src/CryptoEncoding/PEM.php
index 53b46cd5..8d02c560 100644
--- a/src/CryptoEncoding/PEM.php
+++ b/src/CryptoEncoding/PEM.php
@@ -115,7 +115,7 @@ public static function fromFile(string $filename): self
 
         if (!is_readable($filename) || ($str === false)) {
             $e = error_get_last();
-            $error = $e['message'] ?: "Check that the file exists and can be read.";
+            $error = $e['message'] ?? "Check that the file exists and can be read.";
             throw new IOException(sprintf("File '%s' was not loaded;  %s", $filename, $error));
         }
 
diff --git a/src/CryptoEncoding/PEMBundle.php b/src/CryptoEncoding/PEMBundle.php
index 81c90fd5..5ca7a544 100644
--- a/src/CryptoEncoding/PEMBundle.php
+++ b/src/CryptoEncoding/PEMBundle.php
@@ -110,7 +110,7 @@ public static function fromFile(string $filename): self
 
         if (!is_readable($filename) || ($str === false)) {
             $e = error_get_last();
-            $error = $e['message'] ?: "Check that the file exists and can be read.";
+            $error = $e['message'] ?? "Check that the file exists and can be read.";
             throw new IOException(sprintf("File '%s' was not loaded;  %s", $filename, $error));
         }