diff --git a/ext/soap/soap.c b/ext/soap/soap.c
index 17ed373b4398b..d28c77ca9bb68 100644
--- a/ext/soap/soap.c
+++ b/ext/soap/soap.c
@@ -26,6 +26,7 @@
 #include "soap_arginfo.h"
 #include "zend_exceptions.h"
 #include "zend_interfaces.h"
+#include "ext/standard/php_incomplete_class.h"
 
 
 static int le_sdl = 0;
@@ -1330,9 +1331,13 @@ PHP_METHOD(SoapServer, handle)
 			ZVAL_DEREF(session_vars);
 			if (Z_TYPE_P(session_vars) == IS_ARRAY &&
 			    (tmp_soap_p = zend_hash_str_find(Z_ARRVAL_P(session_vars), "_bogus_session_name", sizeof("_bogus_session_name")-1)) != NULL &&
-			    Z_TYPE_P(tmp_soap_p) == IS_OBJECT &&
-			    Z_OBJCE_P(tmp_soap_p) == service->soap_class.ce) {
-				soap_obj = tmp_soap_p;
+			    Z_TYPE_P(tmp_soap_p) == IS_OBJECT) {
+				if (EXPECTED(Z_OBJCE_P(tmp_soap_p) == service->soap_class.ce)) {
+					soap_obj = tmp_soap_p;
+				} else if (Z_OBJCE_P(tmp_soap_p) == php_ce_incomplete_class) {
+					/* See #51561, communicate limitation to user */
+					soap_server_fault("Server", "SoapServer class was deserialized from the session prior to loading the class passed to SoapServer::setClass(). Start the session after loading all classes to resolve this issue.", NULL, NULL, NULL);
+				}
 			}
 		}
 #endif
diff --git a/ext/soap/tests/bugs/bug51561.inc b/ext/soap/tests/bugs/bug51561.inc
new file mode 100644
index 0000000000000..27778d07c5e6c
--- /dev/null
+++ b/ext/soap/tests/bugs/bug51561.inc
@@ -0,0 +1,2 @@
+<?php
+class Server2 {}
diff --git a/ext/soap/tests/bugs/bug51561.phpt b/ext/soap/tests/bugs/bug51561.phpt
new file mode 100644
index 0000000000000..2411ff29e7314
--- /dev/null
+++ b/ext/soap/tests/bugs/bug51561.phpt
@@ -0,0 +1,49 @@
+--TEST--
+Bug #51561 (SoapServer with a extended class and using sessions, lost the setPersistence())
+--EXTENSIONS--
+soap
+--SKIPIF--
+<?php
+    if (!file_exists(__DIR__ . "/../../../../sapi/cli/tests/php_cli_server.inc")) {
+        echo "skip sapi/cli/tests/php_cli_server.inc required but not found";
+    }
+?>
+--FILE--
+<?php
+
+include __DIR__ . "/../../../../sapi/cli/tests/php_cli_server.inc";
+
+$args = ["-d", "extension_dir=" . ini_get("extension_dir"), "-d", "extension=" . (substr(PHP_OS, 0, 3) == "WIN" ? "php_" : "") . "soap." . PHP_SHLIB_SUFFIX];
+if (php_ini_loaded_file()) {
+  // Necessary such that it works from a development directory in which case extension_dir might not be the real extension dir
+  $args[] = "-c";
+  $args[] = php_ini_loaded_file();
+}
+$code = "session_start();" .
+        "require_once '" . __DIR__ . "/bug51561.inc';" .
+        <<<'PHP'
+        class Server extends Server2 {
+            private $value;
+            public function setValue($param) { $this->value = $param; }
+            public function getValue() { return $this->value; }
+        }
+        $server = new SoapServer(null, array('uri' => "blablabla.com",'encoding' => "ISO-8859-1",'soap_version' => SOAP_1_2));
+        $server->setClass("Server");
+        $server->setPersistence(SOAP_PERSISTENCE_SESSION);
+        $server->handle();
+        PHP;
+
+php_cli_server_start($code, null, $args);
+
+$cli = new SoapClient(null, array('location' => "http://".PHP_CLI_SERVER_ADDRESS, 'uri' => "blablabla.com",'encoding' => "ISO-8859-1",'soap_version' => SOAP_1_2));
+$cli->setValue(100);
+$response = $cli->getValue();
+echo "Get = ".$response;	
+
+?>
+--EXPECTF--
+Fatal error: Uncaught SoapFault exception: [env:Receiver] SoapServer class was deserialized from the session prior to loading the class passed to SoapServer::setClass(). Start the session after loading all classes to resolve this issue. in %s:%d
+Stack trace:
+#0 %s(%d): SoapClient->__call('getValue', Array)
+#1 {main}
+  thrown in %s on line %d