diff --git a/intern/cycles/kernel/kernel_bvh.h b/intern/cycles/kernel/kernel_bvh.h
index a1195e424d7..1a85b5bbefd 100644
--- a/intern/cycles/kernel/kernel_bvh.h
+++ b/intern/cycles/kernel/kernel_bvh.h
@@ -929,7 +929,7 @@ __device_inline float3 ray_offset(float3 P, float3 Ng)
 	const float epsilon_f = 1e-5f;
 	/* ideally this should match epsilon_f, but instancing/mblur
 	 * precision makes it problematic */
-	const float epsilon_test = 1e-1f;
+	const float epsilon_test = 1.0f;
 	const int epsilon_i = 32;
 
 	float3 res;
diff --git a/intern/cycles/kernel/kernel_camera.h b/intern/cycles/kernel/kernel_camera.h
index cd896ffe133..f9d5bd3dd3f 100644
--- a/intern/cycles/kernel/kernel_camera.h
+++ b/intern/cycles/kernel/kernel_camera.h
@@ -213,7 +213,7 @@ __device void camera_sample(KernelGlobals *kg, int x, int y, float filter_u, flo
 
 #ifdef __CAMERA_MOTION__
 	/* motion blur */
-	if(kernel_data.cam.shuttertime == 0.0f)
+	if(kernel_data.cam.shuttertime == -1.0f)
 		ray->time = TIME_INVALID;
 	else
 		ray->time = 0.5f + 0.5f*(time - 0.5f)*kernel_data.cam.shuttertime;
diff --git a/intern/cycles/render/camera.cpp b/intern/cycles/render/camera.cpp
index a78ede979b2..3ca19496b72 100644
--- a/intern/cycles/render/camera.cpp
+++ b/intern/cycles/render/camera.cpp
@@ -216,9 +216,9 @@ void Camera::device_update(Device *device, DeviceScene *dscene, Scene *scene)
 
 	/* motion blur */
 #ifdef __CAMERA_MOTION__
-	kcam->shuttertime = (need_motion == Scene::MOTION_BLUR) ? shuttertime: 0.0f;
+	kcam->shuttertime = (need_motion == Scene::MOTION_BLUR) ? shuttertime: -1.0f;
 #else
-	kcam->shuttertime = 0.0f;
+	kcam->shuttertime = -1.0f;
 #endif
 
 	/* type */