diff --git a/NEWS b/NEWS
index d25d441ca8b5..2fc9b3f83766 100644
--- a/NEWS
+++ b/NEWS
@@ -39,6 +39,8 @@ PHP                                                                        NEWS
     with no other live PDO handle. (iliaal)
 
 - Standard:
+  . Fixed GH-23338 (fsockopen()/pfsockopen() ValueError reported wrong
+    argument number for $timeout). (lacatoire)
   . Fixed a memory leak in array_merge_recursive() when the recursive merge of
     an object converted to an array fails. (David Carlier)
 
diff --git a/ext/standard/fsock.c b/ext/standard/fsock.c
index c8e6ed08e4c0..6dd07049e021 100644
--- a/ext/standard/fsock.c
+++ b/ext/standard/fsock.c
@@ -107,7 +107,7 @@ static void php_fsockopen_stream(INTERNAL_FUNCTION_PARAMETERS, int persistent)
 			efree(hashkey);
 		}
 
-		zend_argument_value_error(6, "must be -1 or between 0 and " ZEND_ULONG_FMT, ((double) PHP_TIMEOUT_ULL_MAX / 1000000.0));
+		zend_argument_value_error(5, "must be -1 or between 0 and " ZEND_ULONG_FMT, (zend_ulong)((double) PHP_TIMEOUT_ULL_MAX / 1000000.0));
 		RETURN_THROWS();
 	} else {
 #ifndef PHP_WIN32
diff --git a/ext/standard/tests/network/fsockopen_timeout_out_of_range.phpt b/ext/standard/tests/network/fsockopen_timeout_out_of_range.phpt
new file mode 100644
index 000000000000..575db4690fb9
--- /dev/null
+++ b/ext/standard/tests/network/fsockopen_timeout_out_of_range.phpt
@@ -0,0 +1,19 @@
+--TEST--
+fsockopen() and pfsockopen(): ValueError for $timeout reports correct argument number and name
+--FILE--
+<?php
+try {
+    fsockopen('localhost', 80, $errno, $errstr, -2.0);
+} catch (Throwable $e) {
+    echo $e::class, ': ', $e->getMessage(), "\n";
+}
+
+try {
+    pfsockopen('localhost', 80, $errno, $errstr, -2.0);
+} catch (Throwable $e) {
+    echo $e::class, ': ', $e->getMessage(), "\n";
+}
+?>
+--EXPECTF--
+ValueError: fsockopen(): Argument #5 ($timeout) must be -1 or between 0 and %s
+ValueError: pfsockopen(): Argument #5 ($timeout) must be -1 or between 0 and %s
diff --git a/ext/standard/tests/streams/gh14780.phpt b/ext/standard/tests/streams/gh14780.phpt
index 064e496b1753..c0fc4e621a9d 100644
--- a/ext/standard/tests/streams/gh14780.phpt
+++ b/ext/standard/tests/streams/gh14780.phpt
@@ -31,8 +31,8 @@ try {
 }
 ?>
 --EXPECTF--
-pfsockopen(): Argument #6 must be -1 or between 0 and %s
-pfsockopen(): Argument #6 must be -1 or between 0 and %s
+pfsockopen(): Argument #5 ($timeout) must be -1 or between 0 and %s
+pfsockopen(): Argument #5 ($timeout) must be -1 or between 0 and %s
 resource(%d) of type (persistent stream)
-pfsockopen(): Argument #6 must be -1 or between 0 and %s
-pfsockopen(): Argument #6 must be -1 or between 0 and %s
+pfsockopen(): Argument #5 ($timeout) must be -1 or between 0 and %s
+pfsockopen(): Argument #5 ($timeout) must be -1 or between 0 and %s