diff --git a/apps/seg/Testing/CMakeLists.txt b/apps/seg/Testing/CMakeLists.txt
index 1ead4de9..f31124db 100644
--- a/apps/seg/Testing/CMakeLists.txt
+++ b/apps/seg/Testing/CMakeLists.txt
@@ -50,6 +50,7 @@ dcmqi_add_test(
       --outputDICOM ${MODULE_TEMP_DIR}/liver_heart_seg_reordered.dcm
     )
 
+
 find_program(DCIODVFY_EXECUTABLE dciodvfy)
 
 if(EXISTS ${DCIODVFY_EXECUTABLE})
@@ -139,6 +140,22 @@ dcmqi_add_test(
       ${itk2dcm}_makeSEG_multiple_segment_files_reordered
     )
 
+    dcmqi_add_test(
+      NAME ${dcm2itk}_makeNRRD_merged_segment_file
+      MODULE_NAME ${MODULE_NAME}
+      COMMAND ${SEM_LAUNCH_COMMAND} $<TARGET_FILE:${dcm2itk}Test>
+        --compare ${BASELINE}/liver_seg.nrrd ${MODULE_TEMP_DIR}/makeNRRD_multiple_segments-1.nrrd
+        --compare ${BASELINE}/spine_seg.nrrd ${MODULE_TEMP_DIR}/makeNRRD_multiple_segments-2.nrrd
+        --compare ${BASELINE}/heart_seg.nrrd ${MODULE_TEMP_DIR}/makeNRRD_multiple_segments-3.nrrd
+        ${dcm2itk}Test
+        --inputDICOM ${MODULE_TEMP_DIR}/liver_heart_seg.dcm
+        --outputDirectory ${MODULE_TEMP_DIR}
+        --prefix makeNRRD_merged_segment_file
+        --mergeSegments
+      TEST_DEPENDS
+        ${itk2dcm}_makeSEG_multiple_segment_files
+      )
+
 dcmqi_add_test(
   NAME seg_meta_roundtrip
   MODULE_NAME ${MODULE_NAME}
@@ -160,8 +177,6 @@ dcmqi_add_test(
     ${dcm2itk}_makeNRRD_multiple_segment_files
   )
 
-
-
 set(TEST_SEG_SIZES 24x38x3 23x38x3)
 
 foreach(seg_size ${TEST_SEG_SIZES})
diff --git a/include/dcmqi/JSONSegmentationMetaInformationHandler.h b/include/dcmqi/JSONSegmentationMetaInformationHandler.h
index 1b087a98..c7d312a6 100644
--- a/include/dcmqi/JSONSegmentationMetaInformationHandler.h
+++ b/include/dcmqi/JSONSegmentationMetaInformationHandler.h
@@ -38,7 +38,7 @@ namespace dcmqi {
     // segGroupNumber starts with 0 and refers to the item in segmentsAttributesMappingList.
     // if segGroupNumber is invalid, create segment within a newly created segmentation group
     // otherwise add segment to the existing segmentation group identified by segGroupNumber
-    SegmentAttributes* createOrGetSegment(const int segGroupNumber, unsigned labelID);
+    SegmentAttributes* createOrGetSegment(const unsigned int segGroupNumber, unsigned labelID);
 
   protected:
 
diff --git a/libsrc/JSONSegmentationMetaInformationHandler.cpp b/libsrc/JSONSegmentationMetaInformationHandler.cpp
index 5f6a4d46..8780e7ad 100644
--- a/libsrc/JSONSegmentationMetaInformationHandler.cpp
+++ b/libsrc/JSONSegmentationMetaInformationHandler.cpp
@@ -151,25 +151,21 @@ namespace dcmqi {
     return values;
   }
 
-  SegmentAttributes *JSONSegmentationMetaInformationHandler::createOrGetSegment(const int segGroupNumber, const unsigned labelID) {
-    //std::cout << "DEBUG: num segmentations: " << this->segmentsAttributesMappingList.size() << std::endl;
-    /*
-    for (vector<map<unsigned,SegmentAttributes*> >::const_iterator vIt = this->segmentsAttributesMappingList.begin();
-       vIt != this->segmentsAttributesMappingList.end(); ++vIt) {
-      for(map<unsigned,SegmentAttributes*>::const_iterator mIt = vIt->begin();mIt!=vIt->end();++mIt){
-        SegmentAttributes *segmentAttributes = mIt->second;
-        if (segmentAttributes->getLabelID() == labelID)
-          return NULL;
-      }
-    }*/
+  SegmentAttributes *JSONSegmentationMetaInformationHandler::createOrGetSegment(const unsigned int segGroupNumber, const unsigned labelID) {
+    if (segGroupNumber < 1)
+    {
+      std::cerr << "ERROR: Segment group number must be >= 1" << std::endl;
+      return NULL;
+    }
 
     SegmentAttributes *segment = new SegmentAttributes(labelID);
-    if (this->segmentsAttributesMappingList.size() < segGroupNumber+1) {
+    if (this->segmentsAttributesMappingList.size() < segGroupNumber) {
       map<unsigned,SegmentAttributes*> tempMap;
       tempMap[labelID] = segment;
       this->segmentsAttributesMappingList.push_back(tempMap);
-    } else
-      this->segmentsAttributesMappingList[segGroupNumber][labelID] = segment;
+    } else {
+      this->segmentsAttributesMappingList[segGroupNumber-1][labelID] = segment;
+    }
 
     return segment;
   }
diff --git a/libsrc/OverlapUtil.cpp b/libsrc/OverlapUtil.cpp
index 6e96ceff..a5b77f6c 100644
--- a/libsrc/OverlapUtil.cpp
+++ b/libsrc/OverlapUtil.cpp
@@ -324,7 +324,6 @@ OFCondition OverlapUtil::getSegmentsByPosition(SegmentsByPosition& result)
         DCMSEG_DEBUG(ss.str());
     }
     DCMSEG_DEBUG("groupFramesByPosition(): Grouping segments by position took " << tm.getDiff() << " s");
-
     return cond;
 }