diff --git a/ebtree/ebimtree.h b/ebtree/ebimtree.h
index 1fe9fa0..99e7503 100644
--- a/ebtree/ebimtree.h
+++ b/ebtree/ebimtree.h
@@ -18,6 +18,9 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#ifndef _EBIMTREE_H
+#define _EBIMTREE_H
+
 #include <string.h>
 #include "ebtree.h"
 #include "ebpttree.h"
@@ -317,3 +320,5 @@
 	root->b[side] = eb_dotag(&new->node.branches, EB_NODE);
 	return new;
 }
+
+#endif /* _EBIMTREE_H */
diff --git a/ebtree/ebistree.h b/ebtree/ebistree.h
index a1fbb76..e1bcbc7 100644
--- a/ebtree/ebistree.h
+++ b/ebtree/ebistree.h
@@ -20,6 +20,9 @@
 
 /* These functions and macros rely on Multi-Byte nodes */
 
+#ifndef _EBISTREE_H
+#define _EBISTREE_H
+
 #include <string.h>
 #include "ebtree.h"
 #include "ebpttree.h"
@@ -323,3 +326,4 @@
 	return new;
 }
 
+#endif /* _EBISTREE_H */