diff --git a/pciSeq/src/core/main.py b/pciSeq/src/core/main.py
index 06fc2e16..49e26f29 100644
--- a/pciSeq/src/core/main.py
+++ b/pciSeq/src/core/main.py
@@ -200,7 +200,7 @@ def spots_to_cell(self):
         nN = self.nN
         nS = self.spots.data.gene_name.shape[0]
 
-        wSpotCell = np.zeros([nS, nN], dtype=np.float32)
+        wSpotCell = np.zeros([nS, nN], dtype=np.float64)
         gn = self.spots.data.gene_name.values
         expected_counts = self.single_cell.log_mean_expression.loc[gn].values
         logeta_bar = self.genes.logeta_bar[self.spots.gene_id]