diff --git a/libc/include/sys/param.h b/libc/include/sys/param.h
index 16fed86..79ae067 100644
--- a/libc/include/sys/param.h
+++ b/libc/include/sys/param.h
@@ -51,17 +51,19 @@
 #endif
 #define roundup(x, y)   ((((x)+((y)-1))/(y))*(y))
 
-/*
+/**
  * Returns true if the binary representation of the argument is all zeros
  * or has exactly one bit set. Contrary to the macro name, this macro
  * DOES NOT determine if the provided value is a power of 2. In particular,
  * this function falsely returns true for powerof2(0) and some negative
  * numbers.
  */
-#define powerof2(x) \
-  ({ __typeof__(x) _x = (x); \
-     __typeof__(x) _x2; \
-     __builtin_add_overflow(_x, -1, &_x2) ? 1 : ((_x2&_x) == 0 ); })
+#define powerof2(x)                                               \
+  ({                                                              \
+    __typeof__(x) _x = (x);                                       \
+    __typeof__(x) _x2;                                            \
+    __builtin_add_overflow(_x, -1, &_x2) ? 1 : ((_x2 & _x) == 0); \
+  })
 
 /** Returns the lesser of its two arguments. */
 #define MIN(a,b) (((a)<(b))?(a):(b))