diff --git a/UnitySDK/Assets/ML-Agents/Editor/Tests/RayPerceptionTests.cs b/UnitySDK/Assets/ML-Agents/Editor/Tests/RayPerceptionTests.cs
index dd7ce5745f..21d82f850d 100644
--- a/UnitySDK/Assets/ML-Agents/Editor/Tests/RayPerceptionTests.cs
+++ b/UnitySDK/Assets/ML-Agents/Editor/Tests/RayPerceptionTests.cs
@@ -30,5 +30,11 @@ public void TestPerception2D()
                 tags);
             Assert.IsTrue(result.Count == angles.Length * (tags.Length + 2));
         }
+
+        [Test]
+        public void TestConstants()
+        {
+            Assert.AreEqual(Physics.DefaultRaycastLayers, Physics2D.DefaultRaycastLayers);
+        }
     }
 }
diff --git a/UnitySDK/Assets/ML-Agents/Scripts/Sensor/RayPerceptionSensor.cs b/UnitySDK/Assets/ML-Agents/Scripts/Sensor/RayPerceptionSensor.cs
index ee41a47a58..b0a8cae92f 100644
--- a/UnitySDK/Assets/ML-Agents/Scripts/Sensor/RayPerceptionSensor.cs
+++ b/UnitySDK/Assets/ML-Agents/Scripts/Sensor/RayPerceptionSensor.cs
@@ -25,6 +25,7 @@ public enum CastType
         float m_CastRadius;
         CastType m_CastType;
         Transform m_Transform;
+        int m_LayerMask;
 
         /// <summary>
         /// Debug information for the raycast hits. This is used by the RayPerceptionSensorComponent.
@@ -67,7 +68,8 @@ public DebugDisplayInfo debugDisplayInfo
         }
 
         public RayPerceptionSensor(string name, float rayDistance, List<string> detectableObjects, float[] angles,
-            Transform transform, float startOffset, float endOffset, float castRadius, CastType castType)
+            Transform transform, float startOffset, float endOffset, float castRadius, CastType castType,
+            int rayLayerMask)
         {
             var numObservations = (detectableObjects.Count + 2) * angles.Length;
             m_Shape = new[] { numObservations };
@@ -84,6 +86,7 @@ public RayPerceptionSensor(string name, float rayDistance, List<string> detectab
             m_EndOffset = endOffset;
             m_CastRadius = castRadius;
             m_CastType = castType;
+            m_LayerMask = rayLayerMask;
 
             if (Application.isEditor)
             {
@@ -97,7 +100,8 @@ public int Write(WriteAdapter adapter)
             {
                 PerceiveStatic(
                     m_RayDistance, m_Angles, m_DetectableObjects, m_StartOffset, m_EndOffset,
-                    m_CastRadius, m_Transform, m_CastType, m_Observations, false, m_DebugDisplayInfo
+                    m_CastRadius, m_Transform, m_CastType, m_Observations, false, m_LayerMask,
+                    m_DebugDisplayInfo
                 );
                 adapter.AddRange(m_Observations);
             }
@@ -164,6 +168,7 @@ public static void PerceiveStatic(float rayLength,
             float startOffset, float endOffset, float castRadius,
             Transform transform, CastType castType, float[] perceptionBuffer,
             bool legacyHitFractionBehavior = false,
+            int layerMask = Physics.DefaultRaycastLayers,
             DebugDisplayInfo debugInfo = null)
         {
             Array.Clear(perceptionBuffer, 0, perceptionBuffer.Length);
@@ -221,11 +226,13 @@ public static void PerceiveStatic(float rayLength,
                     RaycastHit rayHit;
                     if (castRadius > 0f)
                     {
-                        castHit = Physics.SphereCast(startPositionWorld, castRadius, rayDirection, out rayHit, rayLength);
+                        castHit = Physics.SphereCast(startPositionWorld, castRadius, rayDirection, out rayHit,
+                            rayLength, layerMask);
                     }
                     else
                     {
-                        castHit = Physics.Raycast(startPositionWorld, rayDirection, out rayHit, rayLength);
+                        castHit = Physics.Raycast(startPositionWorld, rayDirection, out rayHit,
+                            rayLength, layerMask);
                     }
 
                     hitFraction = castHit ? rayHit.distance / rayLength : 1.0f;
@@ -236,11 +243,12 @@ public static void PerceiveStatic(float rayLength,
                     RaycastHit2D rayHit;
                     if (castRadius > 0f)
                     {
-                        rayHit = Physics2D.CircleCast(startPositionWorld, castRadius, rayDirection, rayLength);
+                        rayHit = Physics2D.CircleCast(startPositionWorld, castRadius, rayDirection,
+                            rayLength, layerMask);
                     }
                     else
                     {
-                        rayHit = Physics2D.Raycast(startPositionWorld, rayDirection, rayLength);
+                        rayHit = Physics2D.Raycast(startPositionWorld, rayDirection, rayLength, layerMask);
                     }
 
                     castHit = rayHit;
diff --git a/UnitySDK/Assets/ML-Agents/Scripts/Sensor/RayPerceptionSensorComponentBase.cs b/UnitySDK/Assets/ML-Agents/Scripts/Sensor/RayPerceptionSensorComponentBase.cs
index 7ae5392d0a..669b69d4d6 100644
--- a/UnitySDK/Assets/ML-Agents/Scripts/Sensor/RayPerceptionSensorComponentBase.cs
+++ b/UnitySDK/Assets/ML-Agents/Scripts/Sensor/RayPerceptionSensorComponentBase.cs
@@ -27,6 +27,9 @@ public abstract class RayPerceptionSensorComponentBase : SensorComponent
         [Tooltip("Length of the rays to cast.")]
         public float rayLength = 20f;
 
+        [Tooltip("Controls which layers the rays can hit.")]
+        public LayerMask rayLayerMask = Physics.DefaultRaycastLayers;
+
         [Range(1, 50)]
         [Tooltip("Whether to stack previous observations. Using 1 means no previous observations.")]
         public int observationStacks = 1;
@@ -57,7 +60,8 @@ public override ISensor CreateSensor()
         {
             var rayAngles = GetRayAngles(raysPerDirection, maxRayDegrees);
             m_RaySensor = new RayPerceptionSensor(sensorName, rayLength, detectableTags, rayAngles,
-                transform, GetStartVerticalOffset(), GetEndVerticalOffset(), sphereCastRadius, GetCastType()
+                transform, GetStartVerticalOffset(), GetEndVerticalOffset(), sphereCastRadius, GetCastType(),
+                rayLayerMask
             );
 
             if (observationStacks != 1)
diff --git a/UnitySDK/ProjectSettings/ProjectVersion.txt b/UnitySDK/ProjectSettings/ProjectVersion.txt
index f65e6b3943..2e959fabcf 100755
--- a/UnitySDK/ProjectSettings/ProjectVersion.txt
+++ b/UnitySDK/ProjectSettings/ProjectVersion.txt
@@ -1 +1 @@
-m_EditorVersion: 2017.4.32f1
+m_EditorVersion: 2017.4.33f1