1 files changed, 4 insertions, 0 deletions
diff --git a/trees.h b/trees.h
index 777e1bb..debfbdd 100644
--- a/trees.h
+++ b/trees.h
@@ -1,3 +1,6 @@
+#ifndef TREES_H_
+#define TREES_H_
+
 /* header created automatically with -DGEN_TREES_H */
 
 ZLIB_INTERNAL const ct_data static_ltree[L_CODES+2] = {
@@ -126,3 +129,4 @@ local const int base_dist[D_CODES] = {
  1024,  1536,  2048,  3072,  4096,  6144,  8192, 12288, 16384, 24576
 };
 
+#endif /* TREES_H_ */