diff --git a/loopgen.h b/loopgen.h
index 079c87c..46002dc 100644
--- a/loopgen.h
+++ b/loopgen.h
@@ -2,8 +2,8 @@
  * loopgen.h: interface file for loop generation functions for grid.[ch].
  */
 
-#ifndef _LOOPGEN_H
-#define _LOOPGEN_H
+#ifndef PUZZLES_LOOPGEN_H
+#define PUZZLES_LOOPGEN_H
 
 #include "puzzles.h"
 #include "grid.h"
diff --git a/penrose.h b/penrose.h
index ba5ae16..d1010b9 100644
--- a/penrose.h
+++ b/penrose.h
@@ -10,8 +10,8 @@
  * called with each tile in turn: you choose how many times to recurse.
  */
 
-#ifndef _PENROSE_H
-#define _PENROSE_H
+#ifndef PUZZLES_PENROSE_H
+#define PUZZLES_PENROSE_H
 
 #ifndef PHI
 #define PHI 1.6180339887