diff --git a/include/ucore/utils.h b/include/ucore/utils.h
index f3bedef..39db850 100644
--- a/include/ucore/utils.h
+++ b/include/ucore/utils.h
@@ -14,15 +14,15 @@
 
 //MAX of a and b
 #define UC_MAX(a,b) \
-   ({ __typeof__ (a) _a = (a); \
-       __typeof__ (b) _b = (b); \
-     _a > _b ? _a : _b; })
+   ({ __typeof__ (a) _amx = (a); \
+       __typeof__ (b) _bmx = (b); \
+     _amx > _bmx ? _amx : _bmx; })
 
 //min of a and b
 #define UC_MIN(a,b) \
-   ({ __typeof__ (a) _a = (a); \
-       __typeof__ (b) _b = (b); \
-     _a < _b ? _a : _b; })
+   ({ __typeof__ (a) _amn = (a); \
+       __typeof__ (b) _bmn = (b); \
+     _amn < _bmn ? _amn : _bmn; })
 
 #define ARRAY_SIZE(a) (sizeof(a) / sizeof(*a))