--- a/net/minecraft/util/math/vector/Matrix3f.java
+++ b/net/minecraft/util/math/vector/Matrix3f.java
@@ -444,4 +444,11 @@
    public Matrix3f func_226121_d_() {
       return new Matrix3f(this);
    }
+
+    // Forge start
+    public void multiplyBackward(Matrix3f other) {
+        Matrix3f copy = other.func_226121_d_();
+        copy.func_226118_b_(this);
+        this.func_226114_a_(copy);
+    }
 }
