diff --git a/phpseclib/File/ASN1.php b/phpseclib/File/ASN1.php
index 3b8f11bd..a304a000 100644
--- a/phpseclib/File/ASN1.php
+++ b/phpseclib/File/ASN1.php
@@ -493,6 +493,10 @@ class ASN1
      */
     function asn1map($decoded, $mapping, $special = array())
     {
+        if (!is_array($decoded)) {
+            return false;
+        }
+
         if (isset($mapping['explicit']) && is_array($decoded['content'])) {
             $decoded = $decoded['content'][0];
         }
diff --git a/tests/Unit/File/X509/X509Test.php b/tests/Unit/File/X509/X509Test.php
index 9df21d97..92d756f2 100644
--- a/tests/Unit/File/X509/X509Test.php
+++ b/tests/Unit/File/X509/X509Test.php
@@ -797,4 +797,18 @@ ut3+b2Xvzq8yzmHMFtLIJ6Afu1jJpqD82BUAFcvi5vhnP8M7b974R18WCOpgNQvXDI+2/8ZINeU=
         $r = $x509->loadX509($r);
         $this->assertSame($r['tbsCertificate']['extensions'][5]['extnValue']['excludedSubtrees'][1]['base']['iPAddress'], array('0.0.0.0', '0.0.0.0'));
     }
+
+    /**
+     * @group github1456
+     */
+    public function testRandomString()
+    {
+        $a = 'da7e705569d4196cd49cf3b3d92cd435ca34ccbe';
+        $a = pack('H*', $a);
+
+        $x509 = new File_X509();
+        $r = $x509->loadX509($a);
+
+        $this->assertFalse($r);
+    }
 }