diff --git a/ext/intl/uchar/tests/gh15087.phpt b/ext/intl/uchar/tests/gh15087.phpt
new file mode 100644
index 0000000000000..62009857ab1d6
--- /dev/null
+++ b/ext/intl/uchar/tests/gh15087.phpt
@@ -0,0 +1,10 @@
+--TEST--
+GH-15087 (IntlChar::foldCase()'s $option is not optional)
+--EXTENSIONS--
+intl
+--FILE--
+<?php
+var_dump(IntlChar::foldCase('I'));
+?>
+--EXPECT--
+string(1) "i"
diff --git a/ext/intl/uchar/uchar.c b/ext/intl/uchar/uchar.c
index 771805925827f..7cb6a553af824 100644
--- a/ext/intl/uchar/uchar.c
+++ b/ext/intl/uchar/uchar.c
@@ -392,8 +392,9 @@ IC_METHOD(foldCase) {
 	zend_string *string_codepoint;
 	zend_long int_codepoint;
 
-	ZEND_PARSE_PARAMETERS_START(2, 2)
+	ZEND_PARSE_PARAMETERS_START(1, 2)
 		Z_PARAM_STR_OR_LONG(string_codepoint, int_codepoint)
+		Z_PARAM_OPTIONAL
 		Z_PARAM_LONG(options)
 	ZEND_PARSE_PARAMETERS_END();