diff --git a/ext/mbstring/gen_rare_cp_bitvec.php b/ext/mbstring/gen_rare_cp_bitvec.php
index ca1e85cb3d89a..6f71fd1a2f83a 100755
--- a/ext/mbstring/gen_rare_cp_bitvec.php
+++ b/ext/mbstring/gen_rare_cp_bitvec.php
@@ -6,7 +6,7 @@
     return;
 }
 
-$bitvec = array_fill(0, (0xFFFF / 32) + 1, 0xFFFFFFFF);
+$bitvec = array_fill(0, intdiv(0xFFFF, 32) + 1, 0xFFFFFFFF);
 
 $input = file_get_contents($argv[1]);
 foreach (explode("\n", $input) as $line) {