diff --git a/grbl/planner.c b/grbl/planner.c
index 7989e00..1e0bd35 100644
--- a/grbl/planner.c
+++ b/grbl/planner.c
@@ -277,8 +277,8 @@ uint8_t plan_check_full_buffer()
   #ifdef COREXY
     target_steps[A_MOTOR] = lround(target[A_MOTOR]*settings.steps_per_mm[A_MOTOR]);
     target_steps[B_MOTOR] = lround(target[B_MOTOR]*settings.steps_per_mm[B_MOTOR]);
-    block->steps[A_MOTOR] = labs((target_steps[X_AXIS]-pl.position[X_AXIS]) - (target_steps[Y_AXIS]-pl.position[Y_AXIS]));
-    block->steps[B_MOTOR] = labs((target_steps[X_AXIS]-pl.position[X_AXIS]) + (target_steps[Y_AXIS]-pl.position[Y_AXIS]));
+    block->steps[A_MOTOR] = labs((target_steps[X_AXIS]-pl.position[X_AXIS]) + (target_steps[Y_AXIS]-pl.position[Y_AXIS]));
+    block->steps[B_MOTOR] = labs((target_steps[X_AXIS]-pl.position[X_AXIS]) - (target_steps[Y_AXIS]-pl.position[Y_AXIS]));
   #endif
 
   for (idx=0; idx<N_AXIS; idx++) {
@@ -292,9 +292,9 @@ uint8_t plan_check_full_buffer()
       }
       block->step_event_count = max(block->step_event_count, block->steps[idx]);
       if (idx == A_MOTOR) {
-        delta_mm = ((target_steps[X_AXIS]-pl.position[X_AXIS]) - (target_steps[Y_AXIS]-pl.position[Y_AXIS]))/settings.steps_per_mm[idx];
-      } else if (idx == B_MOTOR) {
         delta_mm = ((target_steps[X_AXIS]-pl.position[X_AXIS]) + (target_steps[Y_AXIS]-pl.position[Y_AXIS]))/settings.steps_per_mm[idx];
+      } else if (idx == B_MOTOR) {
+        delta_mm = ((target_steps[X_AXIS]-pl.position[X_AXIS]) - (target_steps[Y_AXIS]-pl.position[Y_AXIS]))/settings.steps_per_mm[idx];
       } else {
         delta_mm = (target_steps[idx] - pl.position[idx])/settings.steps_per_mm[idx];
       }