diff --git a/libports/include/x86emu/sys/types.h b/libports/include/x86emu/sys/types.h
index 514ae916e..5ac791da9 100644
--- a/libports/include/x86emu/sys/types.h
+++ b/libports/include/x86emu/sys/types.h
@@ -22,4 +22,6 @@ typedef genode_uint32_t uint32_t;
 typedef genode_int64_t   int64_t;
 typedef genode_uint64_t uint64_t;
 
+int abs(int j);
+
 #define NULL (void*)0