diff --git a/src/src/base/ExtendMedicalImageProperties.h b/src/src/base/ExtendMedicalImageProperties.h
index 3d62143..f073fde 100644
--- a/src/src/base/ExtendMedicalImageProperties.h
+++ b/src/src/base/ExtendMedicalImageProperties.h
@@ -41,13 +41,15 @@ public:
 
     long GetSeriesNumberAsLong(){
         if (this->SeriesNumber){
-            return atol(this->SliceThickness);
+            return atol(this->SeriesNumber);
         }
         return 0;
     }
+
     void SetSeriesNumber(long value){
         char buffer [sizeof(long)*8+1];
-        this->SeriesNumber = ltoa(value, buffer, 10);
+        const char* s = ltoa(value, buffer, 10);
+        vtkMedicalImageProperties::SetSeriesNumber(s);
     }