diff --git a/ext/calendar/calendar.c b/ext/calendar/calendar.c
index f26d611092db..5e0cf1381570 100644
--- a/ext/calendar/calendar.c
+++ b/ext/calendar/calendar.c
@@ -550,6 +550,10 @@ PHP_FUNCTION(frenchtojd)
 		RETURN_THROWS();
 	}
 
+	if (year < 1 || year > 14 || month < 1 || month > 13 || day < 1 || day > 30) {
+		RETURN_LONG(0);
+	}
+
 	RETURN_LONG(FrenchToSdn(year, month, day));
 }
 /* }}} */
diff --git a/ext/calendar/tests/frenchtojd_overflow.phpt b/ext/calendar/tests/frenchtojd_overflow.phpt
new file mode 100644
index 000000000000..5091f123d2d9
--- /dev/null
+++ b/ext/calendar/tests/frenchtojd_overflow.phpt
@@ -0,0 +1,29 @@
+--TEST--
+frenchtojd(): out-of-range arguments that alias into valid range via 32-bit narrowing must return 0
+--EXTENSIONS--
+calendar
+--SKIPIF--
+<?php
+if (PHP_INT_SIZE < 8) die("skip 64-bit only");
+?>
+--FILE--
+<?php
+// Values whose low 32 bits land in the valid range must still be rejected.
+// 2**32 == 4294967296; adding it to a valid value produces an alias.
+$bias = 2 ** 32;
+
+// month out of range (aliases to 1)
+var_dump(frenchtojd(1 + $bias, 1, 1));   // month 4294967297 -> 0
+// day out of range (aliases to 1)
+var_dump(frenchtojd(1, 1 + $bias, 1));   // day 4294967297 -> 0
+// year out of range (aliases to 1)
+var_dump(frenchtojd(1, 1, 1 + $bias));   // year 4294967297 -> 0
+
+// Valid call still works
+var_dump(frenchtojd(1, 1, 1));            // int(2375840)
+?>
+--EXPECT--
+int(0)
+int(0)
+int(0)
+int(2375840)