diff --git a/NEWS b/NEWS
index fdbf85be8b4..976713cefdb 100644
--- a/NEWS
+++ b/NEWS
@@ -44,6 +44,9 @@ PHP                                                                        NEWS
   . Fixed bug GH-15711 (SoapClient can't convert BackedEnum to scalar value).
     (nielsdos)
 
+- Standard:
+  . Add support for backed enums in http_build_query(). (ilutov)
+
 12 Sep 2024, PHP 8.4.0beta5
 
 - BCMath:
diff --git a/UPGRADING b/UPGRADING
index ea6f9e79c75..d2965d33966 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -225,6 +225,7 @@ PHP 8.4 UPGRADE NOTES
   . php_uname() now throws ValueErrors on invalid inputs.
   . The "allowed_classes" option for unserialize() now throws TypeErrors and
     ValueErrors if it is not an array of class names.
+  . http_build_query() now correctly handles backed enums.
 
 - Tidy:
   . Failures in the constructor now throw exceptions rather than emitting
diff --git a/ext/standard/http.c b/ext/standard/http.c
index 5f796a4a402..fd862b605a7 100644
--- a/ext/standard/http.c
+++ b/ext/standard/http.c
@@ -20,6 +20,7 @@
 #include "SAPI.h"
 #include "zend_exceptions.h"
 #include "basic_functions.h"
+#include "zend_enum.h"
 
 static void php_url_encode_scalar(zval *scalar, smart_str *form_str,
 	int encoding_type, zend_ulong index_int,
@@ -56,6 +57,7 @@ static void php_url_encode_scalar(zval *scalar, smart_str *form_str,
 	}
 	smart_str_appendc(form_str, '=');
 
+try_again:
 	switch (Z_TYPE_P(scalar)) {
 		case IS_STRING: {
 			zend_string *encoded_data;
@@ -90,6 +92,14 @@ static void php_url_encode_scalar(zval *scalar, smart_str *form_str,
 		case IS_TRUE:
 			smart_str_appendc(form_str, '1');
 			break;
+		case IS_OBJECT:
+			ZEND_ASSERT(Z_OBJCE_P(scalar)->ce_flags & ZEND_ACC_ENUM);
+			if (Z_OBJCE_P(scalar)->enum_backing_type == IS_UNDEF) {
+				zend_value_error("Unbacked enum %s cannot be converted to a string", ZSTR_VAL(Z_OBJCE_P(scalar)->name));
+				return;
+			}
+			scalar = zend_enum_fetch_case_value(Z_OBJ_P(scalar));
+			goto try_again;
 		/* All possible types are either handled here or previously */
 		EMPTY_SWITCH_DEFAULT_CASE();
 	}
@@ -154,7 +164,9 @@ PHPAPI void php_url_encode_hash_ex(HashTable *ht, smart_str *formstr,
 		}
 
 		ZVAL_DEREF(zdata);
-		if (Z_TYPE_P(zdata) == IS_ARRAY || Z_TYPE_P(zdata) == IS_OBJECT) {
+		if (Z_TYPE_P(zdata) == IS_ARRAY
+		 || (Z_TYPE_P(zdata) == IS_OBJECT
+		  && !(Z_OBJCE_P(zdata)->ce_flags & ZEND_ACC_ENUM))) {
 			zend_string *new_prefix;
 			if (key) {
 				zend_string *encoded_key;
@@ -233,6 +245,11 @@ PHP_FUNCTION(http_build_query)
 		Z_PARAM_LONG(enc_type)
 	ZEND_PARSE_PARAMETERS_END();
 
+	if (UNEXPECTED(Z_TYPE_P(formdata) == IS_OBJECT && (Z_OBJCE_P(formdata)->ce_flags & ZEND_ACC_ENUM))) {
+		zend_argument_type_error(1, "must be of type array, %s given", zend_zval_value_name(formdata));
+		RETURN_THROWS();
+	}
+
 	php_url_encode_hash_ex(HASH_OF(formdata), &formstr, prefix, prefix_len, /* key_prefix */ NULL, (Z_TYPE_P(formdata) == IS_OBJECT ? formdata : NULL), arg_sep, (int)enc_type);
 
 	RETURN_STR(smart_str_extract(&formstr));
diff --git a/ext/standard/tests/http/gh15650.phpt b/ext/standard/tests/http/gh15650.phpt
new file mode 100644
index 00000000000..239e0c85164
--- /dev/null
+++ b/ext/standard/tests/http/gh15650.phpt
@@ -0,0 +1,36 @@
+--TEST--
+GH-15650: http_build_query() with enum
+--FILE--
+<?php
+
+enum E1: string {
+    case C = 'hello world!';
+}
+
+enum E2: int {
+    case C = 42;
+}
+
+enum E3 {
+    case C;
+}
+
+echo http_build_query(['e1' => E1::C, 'e2' => E2::C]), "\n";
+
+try {
+    echo http_build_query(['e3' => E3::C]);
+} catch (Throwable $e) {
+    echo get_class($e), ': ', $e->getMessage(), "\n";
+}
+
+try {
+    echo http_build_query(E1::C);
+} catch (Throwable $e) {
+    echo get_class($e), ': ', $e->getMessage(), "\n";
+}
+
+?>
+--EXPECT--
+e1=hello+world%21&e2=42
+ValueError: Unbacked enum E3 cannot be converted to a string
+TypeError: http_build_query(): Argument #1 ($data) must be of type array, E1 given