diff --git a/libc/include/sys/endian.h b/libc/include/sys/endian.h
index cbde121..1186540 100644
--- a/libc/include/sys/endian.h
+++ b/libc/include/sys/endian.h
@@ -186,14 +186,22 @@
 #define letoh64(x) (x)
 #endif /* __BSD_VISIBLE */
 
-#define htons(x) __swap16(x)
+/* glibc compatibility. */
+__BEGIN_DECLS
+uint32_t htonl(uint32_t) __pure2;
+uint16_t htons(uint16_t) __pure2;
+uint32_t ntohl(uint32_t) __pure2;
+uint16_t ntohs(uint16_t) __pure2;
+__END_DECLS
+
 #define htonl(x) __swap32(x)
-#define ntohs(x) __swap16(x)
+#define htons(x) __swap16(x)
 #define ntohl(x) __swap32(x)
+#define ntohs(x) __swap16(x)
 
 /* Bionic additions */
-#define ntohq(x) __swap64(x)
 #define htonq(x) __swap64(x)
+#define ntohq(x) __swap64(x)
 
 #define __LITTLE_ENDIAN_BITFIELD