diff --git a/CMakeLists.txt b/CMakeLists.txt
index c1c7aee6..d35f6cf2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -51,7 +51,8 @@ if(EMSCRIPTEN)
     "-s ALLOW_MEMORY_GROWTH=1 "
     "-s \"EXPORTED_FUNCTIONS=[ "
       "'_main','_lovrDestroy',"
-      "'_mat4_identity','_mat4_invert','_mat4_multiply','_mat4_rotateQuat','_mat4_transform','_mat4_transformDirection',"
+      "'_webvr_onAnimationFrame',"
+      "'_mat4_set','_mat4_identity','_mat4_invert','_mat4_multiply','_mat4_rotateQuat','_mat4_transform','_mat4_transformDirection',"
       "'_quat_fromMat4','_quat_getAngleAxis'"
     "]\" "
     "-s \"EXTRA_EXPORTED_RUNTIME_METHODS=['getValue','setValue']\" "
diff --git a/src/modules/headset/webvr.c b/src/modules/headset/webvr.c
index 7899a108..4b9b4b8f 100644
--- a/src/modules/headset/webvr.c
+++ b/src/modules/headset/webvr.c
@@ -28,7 +28,7 @@ static struct {
   void* renderData;
 } state;
 
-static void webvr_onAnimationFrame(float* leftView, float* rightView, float* leftProjection, float* rightProjection) {
+void webvr_onAnimationFrame(float* leftView, float* rightView, float* leftProjection, float* rightProjection) {
   Camera camera = { .canvas = NULL, .stereo = true };
   memcpy(camera.projection[0], leftProjection, 16 * sizeof(float));
   memcpy(camera.projection[1], rightProjection, 16 * sizeof(float));
diff --git a/src/resources/webvr.js b/src/resources/webvr.js
index 9435dde0..3c52bb2a 100644
--- a/src/resources/webvr.js
+++ b/src/resources/webvr.js
@@ -69,7 +69,8 @@ var LibraryLOVR = {
         HEAPF32[webvr.poseTransform >> 2 + 13] = webvr.offset;
       }
 
-      Module._mat4_invert(Module._mat4_init(e, webvr.poseTransform));
+      Module._mat4_set(e, webvr.poseTransform);
+      Module._mat4_invert(e);
       HEAPF32.set(webvr.frameData.leftViewMatrix, a >> 2);
       HEAPF32.set(webvr.frameData.rightViewMatrix, b >> 2);
       HEAPF32.set(webvr.frameData.leftProjectionMatrix, c >> 2);
@@ -175,7 +176,8 @@ var LibraryLOVR = {
 
     if (pose.orientation) {
       HEAPF32.set(pose.orientation, orientation >> 2);
-      Module._mat4_rotateQuat(Module._mat4_init(webvr.matA, webvr.poseTransform), orientation);
+      Module._mat4_set(webvr.matA, webvr.poseTransform);
+      Module._mat4_rotateQuat(webvr.matA, orientation);
       Module._quat_fromMat4(orientation, webvr.matA);
     } else {
       HEAPF32.fill(0, orientation >> 2, orientation >> 2 + 4);
@@ -297,6 +299,10 @@ var LibraryLOVR = {
     ORIGIN_HEAD: 0,
     ORIGIN_FLOOR: 1,
 
+    // Device
+    DEVICE_HAND_LEFT: 0,
+    DEVICE_HAND_RIGHT: 1,
+
     // DeviceAxis
     AXIS_TRIGGER: 0,
     AXIS_THUMBSTICK: 1,