diff --git a/common/DiffractionExperiment.cpp b/common/DiffractionExperiment.cpp
index 59cdb322..c31b9e0a 100644
--- a/common/DiffractionExperiment.cpp
+++ b/common/DiffractionExperiment.cpp
@@ -52,7 +52,6 @@ DiffractionExperiment::DiffractionExperiment(const DetectorGeometry& geom) {
     dataset.set_compression(JFJochProtoBuf::BSHUF_LZ4);
 
     internal.set_ndatastreams(1);
-    internal.set_nmodules(geom.GetModulesNum());
 
     internal.set_frame_time_us(MIN_FRAME_TIME_HALF_SPEED_IN_US);
     internal.set_count_time_us(MIN_FRAME_TIME_HALF_SPEED_IN_US - READOUT_TIME_IN_US);
@@ -86,7 +85,7 @@ DiffractionExperiment::DiffractionExperiment(const DetectorGeometry& geom) {
 DiffractionExperiment &DiffractionExperiment::Geometry(const DetectorGeometry &input) {
     check_min("Number of modules", input.GetModulesNum(), 1);
     check_max("Number of modules", input.GetModulesNum(), 64); // if operating > 32M, would need to check the code anyway
-
+    internal.set_nmodules(input.GetModulesNum());
     *internal.mutable_conv_geometry() = input;
     return *this;
 }
diff --git a/tests/DiffractionExperimentTest.cpp b/tests/DiffractionExperimentTest.cpp
index 0590044b..086a8a1d 100644
--- a/tests/DiffractionExperimentTest.cpp
+++ b/tests/DiffractionExperimentTest.cpp
@@ -1035,4 +1035,26 @@ TEST_CASE("DiffractionExperiment_Binning","[DiffractionExperiment]") {
     REQUIRE(!x.GetBinning2x2());
     REQUIRE(x.GetXPixelsNum() == RAW_MODULE_COLS);
     REQUIRE(x.GetYPixelsNum() == 8 * RAW_MODULE_LINES);
+}
+
+TEST_CASE("DiffractionExperiment_DetectorModuleHostname","[DiffractionExperiment]") {
+    std::vector<std::string> h = {"mx1", "mx2", "mx3"};
+    DiffractionExperiment x(DetectorGeometry(8));
+    JFJochProtoBuf::DetectorConfig det_cfg;
+
+    JFJochProtoBuf::ReceiverNetworkConfig net_cfg;
+    net_cfg.add_fpga_mac_addr("AA:BB:CC:DD:EE:FF");
+    net_cfg.add_fpga_mac_addr("AA:BB:CC:DD:EE:FE");
+
+    // Before setting module hostname
+    REQUIRE_NOTHROW(det_cfg = x.DetectorConfig(net_cfg));
+
+    REQUIRE_NOTHROW(x.DetectorModuleHostname(h));
+    std::vector<std::string> h_out;
+    REQUIRE_NOTHROW(x.GetDetectorModuleHostname(h_out));
+    REQUIRE(h == h_out);
+
+    REQUIRE_THROWS(det_cfg = x.DetectorConfig(net_cfg));
+    x.Geometry(DetectorGeometry(3));
+    REQUIRE_NOTHROW(det_cfg = x.DetectorConfig(net_cfg));
 }
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