diff --git a/zip_writer.cc b/zip_writer.cc
index 981df3a..0df0fa5 100644
--- a/zip_writer.cc
+++ b/zip_writer.cc
@@ -30,9 +30,13 @@
 #include "entry_name_utils-inl.h"
 #include "zip_archive_common.h"
 
-#if !defined(powerof2)
-#define powerof2(x) ((((x)-1) & (x)) == 0)
-#endif
+#undef powerof2
+#define powerof2(x)                                               \
+  ({                                                              \
+    __typeof__(x) _x = (x);                                       \
+    __typeof__(x) _x2;                                            \
+    __builtin_add_overflow(_x, -1, &_x2) ? 1 : ((_x2 & _x) == 0); \
+  })
 
 /* Zip compression methods we support */
 enum {