diff --git a/NEWS b/NEWS
index 58bbb67f745..3c9a37261ef 100644
--- a/NEWS
+++ b/NEWS
@@ -10,6 +10,10 @@ PHP                                                                        NEWS
   . Fix memory leaks when returning refcounted value from curl callback.
     (nielsdos)
 
+- LDAP:
+  . Fixed GH-18902 ldap_exop/ldap_exop_sync assert triggered on empty
+    request OID. (David Carlier)
+
 - Streams:
   . Fixed GH-13264 (fgets() and stream_get_line() do not return false on filter
     fatal error). (Jakub Zelenka)
diff --git a/ext/ldap/ldap.c b/ext/ldap/ldap.c
index 528f7bc0e12..4712217d0e3 100644
--- a/ext/ldap/ldap.c
+++ b/ext/ldap/ldap.c
@@ -4051,7 +4051,12 @@ static void php_ldap_exop(INTERNAL_FUNCTION_PARAMETERS, bool force_sync) {
 		}
 	}
 
-	if (zend_parse_parameters(ZEND_NUM_ARGS(), "OS|S!a!zz", &link, ldap_link_ce, &reqoid, &reqdata, &serverctrls, &retdata, &retoid) != SUCCESS) {
+	if (zend_parse_parameters(ZEND_NUM_ARGS(), "OP|S!a!zz", &link, ldap_link_ce, &reqoid, &reqdata, &serverctrls, &retdata, &retoid) != SUCCESS) {
+		RETURN_THROWS();
+	}
+
+	if (ZSTR_LEN(reqoid) == 0) {
+		zend_argument_must_not_be_empty_error(2);
 		RETURN_THROWS();
 	}
 
diff --git a/ext/ldap/tests/gh18902.phpt b/ext/ldap/tests/gh18902.phpt
new file mode 100644
index 00000000000..329cbb59c1b
--- /dev/null
+++ b/ext/ldap/tests/gh18902.phpt
@@ -0,0 +1,30 @@
+--TEST--
+GH-17704 (ldap_search fails when $attributes contains a non-packed array with numerical keys)
+--EXTENSIONS--
+ldap
+--FILE--
+<?php
+$conn = ldap_connect();
+
+try {
+	ldap_exop($conn,"\0");
+} catch (\ValueError $e) {
+	echo $e->getMessage(), PHP_EOL;
+}
+
+try {
+	ldap_exop_sync($conn,"");
+} catch (\ValueError $e) {
+	echo $e->getMessage(), PHP_EOL;
+}
+
+try {
+	ldap_exop_sync($conn,"test\0");
+} catch (\ValueError $e) {
+	echo $e->getMessage(), PHP_EOL;
+}
+?>
+--EXPECTF--
+ldap_exop(): Argument #2 ($request_oid) must not contain any null bytes
+ldap_exop_sync(): Argument #2 ($request_oid) must not be empty
+ldap_exop_sync(): Argument #2 ($request_oid) must not contain any null bytes