diff --git a/common/DetectorGeometry.cpp b/common/DetectorGeometry.cpp
index 05243ab1..14f0dfae 100644
--- a/common/DetectorGeometry.cpp
+++ b/common/DetectorGeometry.cpp
@@ -29,6 +29,8 @@ DetectorGeometry::DetectorGeometry(int32_t nmodules, int32_t horizontal_stacking
         throw JFJochException(JFJochExceptionCategory::InputParameterInvalid, "Gap x has to be non-negative");
     if (gap_y < 0)
         throw JFJochException(JFJochExceptionCategory::InputParameterInvalid, "Gap y has to be non-negative");
+    if (nmodules < horizontal_stacking)
+        horizontal_stacking = nmodules;
 
     width = horizontal_stacking * CONVERTED_MODULE_COLS + (horizontal_stacking - 1) * gap_x;
     int64_t conv_lines = nmodules / horizontal_stacking + (nmodules % horizontal_stacking > 0 ? 1 : 0);
diff --git a/tests/DetectorGeometryTest.cpp b/tests/DetectorGeometryTest.cpp
index d3ff8981..0b70958c 100644
--- a/tests/DetectorGeometryTest.cpp
+++ b/tests/DetectorGeometryTest.cpp
@@ -20,6 +20,20 @@ TEST_CASE("DetectorGeometry_Regular", "[DetectorGeometry]") {
     REQUIRE(pbuf.module_geometry(15).slow_direction_step() == pbuf.width_pxl());
 }
 
+TEST_CASE("DetectorGeometry_Regular_1Module", "[DetectorGeometry]") {
+    DetectorGeometry geometry(1, 3, 8, 36, false);
+
+    const JFJochProtoBuf::DetectorGeometry pbuf = geometry;
+    REQUIRE(pbuf.module_geometry_size() == 1);
+
+    REQUIRE(pbuf.width_pxl() == CONVERTED_MODULE_COLS);
+    REQUIRE(pbuf.height_pxl() == CONVERTED_MODULE_LINES);
+    REQUIRE(pbuf.module_geometry(0).pixel0() == 0);
+
+    REQUIRE(pbuf.module_geometry(0).fast_direction_step() == 1);
+    REQUIRE(pbuf.module_geometry(0).slow_direction_step() == CONVERTED_MODULE_COLS);
+}
+
 TEST_CASE("DetectorGeometry_RegularMirror", "[DetectorGeometry]") {
     DetectorGeometry geometry(18, 3, 8, 36, true);