diff --git a/extensions-builtin/forge_preprocessor_reference/scripts/forge_reference.py b/extensions-builtin/forge_preprocessor_reference/scripts/forge_reference.py
index 68be9fb9..e4469975 100644
--- a/extensions-builtin/forge_preprocessor_reference/scripts/forge_reference.py
+++ b/extensions-builtin/forge_preprocessor_reference/scripts/forge_reference.py
@@ -7,14 +7,28 @@ import ldm_patched.ldm.modules.attention as attention
 
 
 def sdp(q, k, v, transformer_options):
+    if q.shape[0] == 0:
+        return q
+
     return attention.optimized_attention(q, k, v, heads=transformer_options["n_heads"], mask=None)
 
 
 def adain(x, target_std, target_mean):
+    if x.shape[0] == 0:
+        return x
+
     std, mean = torch.std_mean(x, dim=(2, 3), keepdim=True, correction=0)
     return (((x - mean) / std) * target_std) + target_mean
 
 
+def zero_cat(a, b, dim):
+    if a.shape[0] == 0:
+        return b
+    if b.shape[0] == 0:
+        return a
+    return torch.cat([a, b], dim=dim)
+
+
 class PreprocessorReference(Preprocessor):
     def __init__(self, name, use_attn=True, use_adain=True, priority=0):
         super().__init__()
@@ -84,7 +98,7 @@ class PreprocessorReference(Preprocessor):
                 return h
 
             channel = int(h.shape[1])
-            minimal_channel = 1280 - 640 * weight
+            minimal_channel = 1500 - 1000 * weight
 
             if channel < minimal_channel:
                 return h
@@ -128,7 +142,7 @@ class PreprocessorReference(Preprocessor):
                         transformer_options['block_index'])
 
             channel = int(q.shape[2])
-            minimal_channel = 1280 - 1280 * weight
+            minimal_channel = 1500 - 1280 * weight
 
             if channel < minimal_channel:
                 return sdp(q, k, v, transformer_options)
@@ -152,9 +166,9 @@ class PreprocessorReference(Preprocessor):
 
                 k_r, v_r = self.recorded_attn1[location]
 
-                o_c = sdp(q_c, torch.cat([k_c, k_r], dim=1), torch.cat([v_c, v_r], dim=1), transformer_options)
+                o_c = sdp(q_c, zero_cat(k_c, k_r, dim=1), zero_cat(v_c, v_r, dim=1), transformer_options)
                 o_uc_strong = sdp(q_uc, k_uc, v_uc, transformer_options)
-                o_uc_weak = sdp(q_uc, torch.cat([k_uc, k_r], dim=1), torch.cat([v_uc, v_r], dim=1), transformer_options)
+                o_uc_weak = sdp(q_uc, zero_cat(k_uc, k_r, dim=1), zero_cat(v_uc, v_r, dim=1), transformer_options)
                 o_uc = o_uc_weak + (o_uc_strong - o_uc_weak) * style_fidelity
 
                 recon = []