diff --git a/gtsam/CMakeLists.txt b/gtsam/CMakeLists.txt
index 845ac7cd0..09f1ea806 100644
--- a/gtsam/CMakeLists.txt
+++ b/gtsam/CMakeLists.txt
@@ -10,7 +10,7 @@ set (gtsam_subdirs
     inference
     symbolic
     discrete
-	hybrid
+    hybrid
     linear
     nonlinear
     sam
diff --git a/gtsam/hybrid/CGMixtureFactor.h b/gtsam/hybrid/CGMixtureFactor.h
index 0528d5401..556c53cc5 100644
--- a/gtsam/hybrid/CGMixtureFactor.h
+++ b/gtsam/hybrid/CGMixtureFactor.h
@@ -18,6 +18,8 @@
  * @date   Mar 12, 2022
  */
 
+#pragma once
+
 #include <gtsam/discrete/DecisionTree.h>
 #include <gtsam/discrete/DiscreteKey.h>
 #include <gtsam/hybrid/HybridFactor.h>
diff --git a/gtsam/hybrid/CLGaussianConditional.h b/gtsam/hybrid/CLGaussianConditional.h
index 0429f4835..d80cb804f 100644
--- a/gtsam/hybrid/CLGaussianConditional.h
+++ b/gtsam/hybrid/CLGaussianConditional.h
@@ -16,6 +16,8 @@
  * @date   Mar 12, 2022
  */
 
+#pragma once
+
 #include <gtsam/discrete/DecisionTree.h>
 #include <gtsam/hybrid/HybridFactor.h>
 #include <gtsam/inference/Conditional.h>
diff --git a/gtsam/hybrid/HybridDiscreteFactor.h b/gtsam/hybrid/HybridDiscreteFactor.h
index 09da9cf70..f182f90a9 100644
--- a/gtsam/hybrid/HybridDiscreteFactor.h
+++ b/gtsam/hybrid/HybridDiscreteFactor.h
@@ -15,6 +15,8 @@
  *  @author Fan Jiang
  */
 
+#pragma once
+
 #include <gtsam/discrete/DecisionTreeFactor.h>
 #include <gtsam/discrete/DiscreteFactor.h>
 #include <gtsam/hybrid/HybridFactor.h>
diff --git a/gtsam/hybrid/HybridGaussianFactor.h b/gtsam/hybrid/HybridGaussianFactor.h
index 23a3c0110..03c49564e 100644
--- a/gtsam/hybrid/HybridGaussianFactor.h
+++ b/gtsam/hybrid/HybridGaussianFactor.h
@@ -15,6 +15,8 @@
  *  @author Fan Jiang
  */
 
+#pragma once
+
 #include <gtsam/hybrid/HybridFactor.h>
 #include <gtsam/linear/GaussianFactor.h>
 #include <gtsam/linear/JacobianFactor.h>