diff --git a/src/os_mac_conv.c b/src/os_mac_conv.c
index 2bd337e..211e115 100644
--- a/src/os_mac_conv.c
+++ b/src/os_mac_conv.c
@@ -550,7 +550,7 @@
     }
 
     convertRange = CFRangeMake(0, CFStringGetLength(utf8_str));
-    result = (UniChar *)alloc(convertRange.length * sizeof(UniChar));
+    result = ALLOC_MULT(UniChar, convertRange.length);
 
     CFStringGetCharacters(utf8_str, convertRange, result);