--- libgeis/backend/grail/geis_grail_backend.c
+++ libgeis/backend/grail/geis_grail_backend.c
@@ -203,7 +203,19 @@
                                            GEIS_ATTR_TYPE_STRING,
                                            "n/a"));
 
-  geis_frame_set_matrix(frame, &(*C)[0][0]);
+  // grail gives us a 3x3 matrix but geis_frame_set_matrix expects a
+  // 4x4 matrix, so we need to convert this.
+  GeisFloat D[16];
+  memset(D, 0, sizeof(D));
+  // We fill the left upper 3x3 submatrix of our 4x4 matrix.
+  for (unsigned int col = 0; col < 3; ++col)
+    for (unsigned int row = 0; row < 3; ++row)
+      D[4 * row + col] = (*C)[row][col];
+  // As usual for transformation matrices, the lower right entry needs
+  // to be 1.
+  D[15] = 1;
+
+  geis_frame_set_matrix(frame, D);
   if (ugmask & UGGestureTypeDrag)
   {
     geis_frame_set_is_class(frame, gbe->drag_class);