diff --git a/compat/arc4random.c b/compat/arc4random.c
index 2c859f184..a09665c5d 100644
--- a/compat/arc4random.c
+++ b/compat/arc4random.c
@@ -48,6 +48,9 @@
 #else				/* !__GNUC__ */
 #define inline
 #endif				/* !__GNUC__ */
+#ifndef MAP_ANON
+#define MAP_ANON MAP_ANONYMOUS
+#endif
 
 #define KEYSZ	32
 #define IVSZ	8
diff --git a/compat/getentropy_linux.c b/compat/getentropy_linux.c
index f8c5e0f7e..b86c0fba2 100644
--- a/compat/getentropy_linux.c
+++ b/compat/getentropy_linux.c
@@ -60,6 +60,9 @@
 #include <sys/auxv.h>
 #endif
 #include <sys/vfs.h>
+#ifndef MAP_ANON
+#define MAP_ANON MAP_ANONYMOUS
+#endif
 
 #define REPEAT 5
 #define min(a, b) (((a) < (b)) ? (a) : (b))
diff --git a/doc/Changelog b/doc/Changelog
index 2f289cae4..aad850cae 100644
--- a/doc/Changelog
+++ b/doc/Changelog
@@ -3,7 +3,8 @@
 	  null delete for wsaevent.
 	- Fix spelling in freebind option man page text.
 	- Fix windows link of ssl with crypt32.
-	- Fix 779:  Union casting is non-portable.
+	- Fix 779: Union casting is non-portable.
+	- Fix 780: MAP_ANON not defined in HP-UX 11.31.
 
 13 June 2016: Ralph
 	- Use QTYPE=A for QNAME minimisation.