diff --git a/include/shred.h b/include/shred.h
index 1d9af23..635f265 100644
--- a/include/shred.h
+++ b/include/shred.h
@@ -47,7 +47,7 @@ private:
 
     inline double calcProgress();
     int iRewindDrive(fileDescriptor file);
-    unsigned long getDriveSizeInBytes(fileDescriptor file);
+    long getDriveSizeInBytes(fileDescriptor file);
     unsigned int uiCalcChecksum(fileDescriptor file, Drive *drive, int *ipSignalFd);
     void cleanup();
 };
diff --git a/src/shred.cpp b/src/shred.cpp
index 8fd3fae..906e908 100644
--- a/src/shred.cpp
+++ b/src/shred.cpp
@@ -239,19 +239,25 @@ int Shred::iRewindDrive(fileDescriptor file)
     }
 }
 
-unsigned long Shred::getDriveSizeInBytes(fileDescriptor file)
+long Shred::getDriveSizeInBytes(fileDescriptor file)
 {
-    unsigned long ulDriveSizeTmp = lseek(file, 0L, SEEK_END);
+    long liDriveSizeTmp = lseek(file, 0L, SEEK_END);
+
+    if (liDriveSizeTmp == -1)
+    {
+        perror("unable to get drive size");
+        return 0L;
+    }
 
     if (0 != iRewindDrive(file))
     {
-        ulDriveSizeTmp = 0U;
+        liDriveSizeTmp = 0L;
     }
 
 #ifdef DEMO_DRIVE_SIZE
-    ulDriveSizeTmp = DEMO_DRIVE_SIZE;
+    liDriveSizeTmp = DEMO_DRIVE_SIZE;
 #endif
-    return ulDriveSizeTmp;
+    return liDriveSizeTmp;
 }
 
 unsigned int Shred::uiCalcChecksum(fileDescriptor file, Drive *drive, int *ipSignalFd)