diff --git a/src/includes_normalize.h b/src/includes_normalize.h
index 7d505564ad..8d29a64a93 100644
--- a/src/includes_normalize.h
+++ b/src/includes_normalize.h
@@ -12,6 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#ifndef INCLUDES_NORMALIZE_H_
+#define INCLUDES_NORMALIZE_H_
+
 #include <string>
 #include <vector>
 
@@ -38,3 +41,5 @@ struct IncludesNormalize {
   std::string relative_to_;
   std::vector<StringPiece> split_relative_to_;
 };
+
+#endif  // INCLUDES_NORMALIZE_H_
diff --git a/src/msvc_helper.h b/src/msvc_helper.h
index 568b9f94e5..699b0a132d 100644
--- a/src/msvc_helper.h
+++ b/src/msvc_helper.h
@@ -12,6 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#ifndef MSVC_HELPER_H_
+#define MSVC_HELPER_H_
+
 #include <string>
 
 std::string EscapeForDepfile(const std::string& path);
@@ -30,3 +33,5 @@ struct CLWrapper {
 
   void* env_block_;
 };
+
+#endif  // MSVC_HELPER_H_