diff --git a/src/zcl_excel_graph.clas.abap b/src/zcl_excel_graph.clas.abap
index a74e270..39272ea 100644
--- a/src/zcl_excel_graph.clas.abap
+++ b/src/zcl_excel_graph.clas.abap
@@ -348,8 +348,8 @@ CLASS zcl_excel_graph IMPLEMENTATION.
   METHOD create_serie.
     DATA ls_serie TYPE s_series.
 
-    DATA: lv_start_row_c TYPE char7,
-          lv_stop_row_c  TYPE char7.
+    DATA: lv_start_row_c TYPE c LENGTH 7,
+          lv_stop_row_c  TYPE c LENGTH 7.
 
 
     IF ip_lbl IS NOT SUPPLIED.
diff --git a/src/zcl_excel_range.clas.abap b/src/zcl_excel_range.clas.abap
index a3d1bcb..ea5feec 100644
--- a/src/zcl_excel_range.clas.abap
+++ b/src/zcl_excel_range.clas.abap
@@ -62,8 +62,8 @@ CLASS zcl_excel_range IMPLEMENTATION.
 
 
   METHOD set_value.
-    DATA: lv_start_row_c TYPE char7,
-          lv_stop_row_c  TYPE char7,
+    DATA: lv_start_row_c TYPE c LENGTH 7,
+          lv_stop_row_c  TYPE c LENGTH 7,
           lv_value       TYPE string.
     lv_stop_row_c = ip_stop_row.
     SHIFT lv_stop_row_c RIGHT DELETING TRAILING space.