diff --git a/libc/kernel/uapi/asm-generic/bitsperlong.h b/libc/kernel/uapi/asm-generic/bitsperlong.h
index 8fb379f..e8945e3 100644
--- a/libc/kernel/uapi/asm-generic/bitsperlong.h
+++ b/libc/kernel/uapi/asm-generic/bitsperlong.h
@@ -19,6 +19,10 @@
 #ifndef _UAPI__ASM_GENERIC_BITS_PER_LONG
 #define _UAPI__ASM_GENERIC_BITS_PER_LONG
 #ifndef __BITS_PER_LONG
+#if defined(__CHAR_BIT__) && defined(__SIZEOF_LONG__)
+#define __BITS_PER_LONG (__CHAR_BIT__ * __SIZEOF_LONG__)
+#else
 #define __BITS_PER_LONG 32
 #endif
 #endif
+#endif