diff --git a/pySDC/helpers/spectral_helper.py b/pySDC/helpers/spectral_helper.py
index 7381b33e6..0ec096707 100644
--- a/pySDC/helpers/spectral_helper.py
+++ b/pySDC/helpers/spectral_helper.py
@@ -882,6 +882,7 @@ def __init__(self, comm=None, useGPU=False, debug=False):
         self.BCs = None
 
         self.fft_cache = {}
+        self.fft_dealias_shape_cache = {}
 
     @property
     def u_init(self):
@@ -1470,7 +1471,9 @@ def _transform_dct(self, u, axes, padding=None, **kwargs):
 
             if padding is not None:
                 shape = list(v.shape)
-                if self.comm:
+                if ('forward', *padding) in self.fft_dealias_shape_cache.keys():
+                    shape[0] = self.fft_dealias_shape_cache[('forward', *padding)]
+                elif self.comm:
                     send_buf = np.array(v.shape[0])
                     recv_buf = np.array(v.shape[0])
                     self.comm.Allreduce(send_buf, recv_buf)
@@ -1645,7 +1648,9 @@ def _transform_idct(self, u, axes, padding=None, **kwargs):
             if padding is not None:
                 if padding[axis] != 1:
                     shape = list(v.shape)
-                    if self.comm:
+                    if ('backward', *padding) in self.fft_dealias_shape_cache.keys():
+                        shape[0] = self.fft_dealias_shape_cache[('backward', *padding)]
+                    elif self.comm:
                         send_buf = np.array(v.shape[0])
                         recv_buf = np.array(v.shape[0])
                         self.comm.Allreduce(send_buf, recv_buf)