diff --git a/main_moco.py b/main_moco.py
index d7ea97359..c2f9f0022 100755
--- a/main_moco.py
+++ b/main_moco.py
@@ -158,7 +158,7 @@ def print_pass(*args):
     print("=> creating model '{}'".format(args.arch))
     model = moco.builder.MoCo(
         models.__dict__[args.arch],
-        args.moco_dim, args.moco_k, args.moco_m, args.moco_t, args.mlp)
+        args.moco_dim, args.moco_k, args.moco_m, args.moco_t, args.mlp, args.batch_size)
     print(model)
 
     if args.distributed:
diff --git a/moco/builder.py b/moco/builder.py
index 7d80fe996..96855ad24 100644
--- a/moco/builder.py
+++ b/moco/builder.py
@@ -8,7 +8,7 @@ class MoCo(nn.Module):
     Build a MoCo model with: a query encoder, a key encoder, and a queue
     https://arxiv.org/abs/1911.05722
     """
-    def __init__(self, base_encoder, dim=128, K=65536, m=0.999, T=0.07, mlp=False):
+    def __init__(self, base_encoder, dim=128, K=65536, m=0.999, T=0.07, mlp=False, fixed_batch_size = 256):
         """
         dim: feature dimension (default: 128)
         K: queue size; number of negative keys (default: 65536)
@@ -20,6 +20,7 @@ def __init__(self, base_encoder, dim=128, K=65536, m=0.999, T=0.07, mlp=False):
         self.K = K
         self.m = m
         self.T = T
+        self.fixed_batch_size = fixed_batch_size
 
         # create the encoders
         # num_classes is the output fc dimension
@@ -57,11 +58,11 @@ def _dequeue_and_enqueue(self, keys):
         batch_size = keys.shape[0]
 
         ptr = int(self.queue_ptr)
-        assert self.K % batch_size == 0  # for simplicity
+        assert self.K % self.fixed_batch_size == 0  # for simplicity
 
         # replace the keys at ptr (dequeue and enqueue)
         self.queue[:, ptr:ptr + batch_size] = keys.T
-        ptr = (ptr + batch_size) % self.K  # move pointer
+        ptr = (ptr + self.fixed_batch_size) % self.K  # move pointer
 
         self.queue_ptr[0] = ptr