diff --git a/phpseclib/Crypt/Common/Formats/Keys/PKCS8.php b/phpseclib/Crypt/Common/Formats/Keys/PKCS8.php
index 8d0f950e..f8c199de 100644
--- a/phpseclib/Crypt/Common/Formats/Keys/PKCS8.php
+++ b/phpseclib/Crypt/Common/Formats/Keys/PKCS8.php
@@ -513,7 +513,7 @@ abstract class PKCS8 extends PKCS
             return $public;
         }
 
-        return false;
+        throw new \RuntimeException('Unable to parse using either OneAsymmetricKey or PublicKeyInfo ASN1 maps');
     }
 
     /**
diff --git a/phpseclib/Crypt/RSA.php b/phpseclib/Crypt/RSA.php
index 431eb5fd..dd3c3e71 100644
--- a/phpseclib/Crypt/RSA.php
+++ b/phpseclib/Crypt/RSA.php
@@ -412,7 +412,7 @@ abstract class RSA extends AsymmetricKey
         $key->publicExponent = $components['publicExponent'];
         $key->k = $key->modulus->getLengthInBytes();
 
-        if ($components['isPublicKey']) {
+        if ($components['isPublicKey'] || !isset($components['privateExponent'])) {
             $key->exponent = $key->publicExponent;
         } else {
             $key->privateExponent = $components['privateExponent'];
diff --git a/tests/Unit/Crypt/RSA/LoadKeyTest.php b/tests/Unit/Crypt/RSA/LoadKeyTest.php
index 48331e8c..f2fe3e0c 100644
--- a/tests/Unit/Crypt/RSA/LoadKeyTest.php
+++ b/tests/Unit/Crypt/RSA/LoadKeyTest.php
@@ -1033,4 +1033,16 @@ v/Ow5T0q5gIJAiEAyS4RaI9YG8EWx/2w0T67ZUVAw8eOMB6BIUg0Xcu+3okCIBOs
         $key = PublicKeyLoader::load($key);
         $key->withPassword('demo')->toString('XML');
     }
+
+    public function testPublicAsPrivatePKCS1()
+    {
+        $key = '-----BEGIN RSA PRIVATE KEY-----
+MIGJAoGBANOV2sOh8KgK9ENJMCzkIQ+UogWU7GP4JMpGxT6aEoxE3O5zUo2D1asv
+RrnqAxlf1zz+1dnRDU8EYbt+DJMLJ5pBeDbBuQzzV690+f7eporcZombSN2JoPAM
+n9dyFZYXxil/cgFG/PDMnuXy1Wcl8hb8iwQag4Y7ohiLXVTJa/0BAgMBAAE=
+-----END RSA PRIVATE KEY-----';
+        $key = PublicKeyLoader::load($key);
+        $result = $key->toString('PKCS1');
+        $this->assertInternalType('string', $result);
+    }
 }