diff --git a/cxxmph/bm_common.h b/cxxmph/bm_common.h
index ad8466e..4fea687 100644
--- a/cxxmph/bm_common.h
+++ b/cxxmph/bm_common.h
@@ -1,3 +1,6 @@
+#ifndef __CXXMPH_BM_COMMON_H__
+#define __CXXMPH_BM_COMMON_H__
+
 #include "stringpiece.h"
 
 #include <string>
@@ -58,3 +61,5 @@ class SearchUint64Benchmark : public Uint64Benchmark {
 };
 
 }  // namespace cxxmph
+
+#endif  // __CXXMPH_BM_COMMON_H__
diff --git a/cxxmph/mph_map.h b/cxxmph/mph_map.h
index 23407d4..ddb8268 100644
--- a/cxxmph/mph_map.h
+++ b/cxxmph/mph_map.h
@@ -1,3 +1,5 @@
+#ifndef __CXXMPH_MPH_MAP_H__
+#define __CXXMPH_MPH_MAP_H__
 // Implementation of the unordered associative mapping interface using a
 // minimal perfect hash function.
 //
@@ -191,3 +193,5 @@ MPH_MAP_METHOD_DECL(data_type&, operator[])(const key_type& k) {
 }
 
 }  // namespace cxxmph
+
+#endif  // __CXXMPH_MPH_MAP_H__