diff --git a/matrices.h b/matrices.h
index ef42bbd..3ca3ace 100644
--- a/matrices.h
+++ b/matrices.h
@@ -1,3 +1,6 @@
+#ifndef MATRICES_H_
+#define MATRICES_H_
+
 #include <string>
 #include <vector>
 #include <cassert>
@@ -258,4 +261,6 @@ void Matrix::Randomize(float min, float max){
             this->values[m][n] = min + ((float)rand()/(float)(RAND_MAX)) * (max - min);
         }
     }
-}
\ No newline at end of file
+}
+
+#endif
\ No newline at end of file