diff --git a/fpga/hls/hls_jfjoch.h b/fpga/hls/hls_jfjoch.h
index 5332e2a8..3e6cef7c 100644
--- a/fpga/hls/hls_jfjoch.h
+++ b/fpga/hls/hls_jfjoch.h
@@ -200,7 +200,7 @@ void spot_finder(STREAM_512 &data_in,
                  STREAM_512 &data_out,
                  hls::stream<ap_axiu<32,1,1,1>> &strong_pixel_out,
                  volatile ap_int<16> &in_photon_count_threshold,
-                 volatile strong_pixel_threshold_t &in_strong_pixel_threshold);
+                 volatile ap_uint<16> &in_strong_pixel_threshold);
 
 void adu_histo(STREAM_512 &data_in,
                STREAM_512 &data_out,
diff --git a/fpga/hls/spot_finder.cpp b/fpga/hls/spot_finder.cpp
index 511ed5ef..1c3108a3 100644
--- a/fpga/hls/spot_finder.cpp
+++ b/fpga/hls/spot_finder.cpp
@@ -308,6 +308,17 @@ void spot_finder_line_sum_align(hls::stream<spot_finder_packet> &data_in,
     data_out << packet_in;
 }
 
+strong_pixel_threshold_t calculate_threshold(volatile ap_uint<16> &in_strong_pixel_threshold) {
+#pragma HLS INLINE
+    ap_uint<16> tmp = in_strong_pixel_threshold;
+    strong_pixel_threshold_t strong_pixel_threshold = 0;
+    for (int i = 0; i < 16; i++) {
+#pragma HLS UNROLL
+        strong_pixel_threshold[i] = tmp[i];
+    }
+    return strong_pixel_threshold * strong_pixel_threshold;
+}
+
 void spot_finder_check_threshold(hls::stream<spot_finder_packet> &data_in,
                                  STREAM_512 &data_out,
                                  hls::stream<ap_uint<SUM_BITWIDTH*32>> &sum_in,
@@ -315,7 +326,7 @@ void spot_finder_check_threshold(hls::stream<spot_finder_packet> &data_in,
                                  hls::stream<ap_uint<MASK_SUM_BITWIDTH*32>> &valid_in,
                                  hls::stream<ap_axiu<32,1,1,1>> &strong_pixel_out,
                                  volatile ap_int<16> &in_photon_count_threshold,
-                                 volatile strong_pixel_threshold_t &in_strong_pixel_threshold) {
+                                 volatile ap_uint<16> &in_strong_pixel_threshold) {
     spot_finder_packet packet_in;
     data_in >> packet_in;
     data_out << packet_512_t{.data=packet_in.data, .user=0, .last=0};
@@ -326,8 +337,7 @@ void spot_finder_check_threshold(hls::stream<spot_finder_packet> &data_in,
     data_in >> packet_in;
     while (!packet_in.user) {
         ap_int<16> photon_count_threshold = in_photon_count_threshold;
-        strong_pixel_threshold_t strong_pixel_threshold = in_strong_pixel_threshold;
-        strong_pixel_threshold_t strong_pixel_threshold_sq = strong_pixel_threshold * strong_pixel_threshold;
+        strong_pixel_threshold_t strong_pixel_threshold_sq = calculate_threshold(in_strong_pixel_threshold);
         for (int i = 0; i < RAW_MODULE_SIZE * sizeof(uint16_t) / 64; i++) {
 #pragma HLS PIPELINE II=1
             data_out << packet_512_t{.data=packet_in.data, .user=0, .last=0};
@@ -350,7 +360,7 @@ void spot_finder(STREAM_512 &data_in,
                  STREAM_512 &data_out,
                  hls::stream<ap_axiu<32,1,1,1>> &strong_pixel_out,
                  volatile ap_int<16> &in_photon_count_threshold,
-                 volatile strong_pixel_threshold_t &in_strong_pixel_threshold) {
+                 volatile ap_uint<16> &in_strong_pixel_threshold) {
 #pragma HLS INTERFACE ap_ctrl_none port=return
 #pragma HLS DATAFLOW
 
diff --git a/fpga/hls/spot_finder.h b/fpga/hls/spot_finder.h
index b9bfff4d..34b07499 100644
--- a/fpga/hls/spot_finder.h
+++ b/fpga/hls/spot_finder.h
@@ -137,7 +137,7 @@ void spot_finder_check_threshold(hls::stream<spot_finder_packet> &data_in,
                                  hls::stream<ap_uint<MASK_SUM_BITWIDTH*32>> &valid_in,
                                  hls::stream<ap_axiu<32,1,1,1>> &strong_pixel_out,
                                  volatile ap_int<16> &in_photon_count_threshold,
-                                 volatile strong_pixel_threshold_t &in_strong_pixel_threshold);
+                                 volatile ap_uint<16> &in_strong_pixel_threshold);
 
 ap_uint<32> check_threshold(const ap_uint<512> data_packed,
                             const ap_uint<SUM_BITWIDTH*32> sum_packed,
diff --git a/receiver/HLSSimulatedDevice.cpp b/receiver/HLSSimulatedDevice.cpp
index 50339526..5e0981dc 100644
--- a/receiver/HLSSimulatedDevice.cpp
+++ b/receiver/HLSSimulatedDevice.cpp
@@ -349,7 +349,7 @@ void HLSSimulatedDevice::HLSMainThread() {
 
 
     ap_int<16> photon_count_threshold = 5;
-    strong_pixel_threshold_t strong_pixel_threshold = 7;
+    ap_uint<16> strong_pixel_threshold = 7;
 
     // 6. Spot finding
     hls_cores.emplace_back([&] { spot_finder(converted_5, converted_6,