diff --git a/dap/algos/spiana.py b/dap/algos/spiana.py
index 6cbd2dc..e3d3686 100644
--- a/dap/algos/spiana.py
+++ b/dap/algos/spiana.py
@@ -36,7 +36,7 @@ def calc_spi_analysis(results, data):
     hit = (photon_percentage > spi_threshold_hit_percentage)
 
     results["number_of_spots"] = photon_percentage
-    results["is_hit_frame"] = hit
+    results["is_hit_frame"] = bool(hit) # json does not like numpy bool_ scalars