diff --git a/src/read_workbook.cpp b/src/read_workbook.cpp
index a83456f..be03711 100644
--- a/src/read_workbook.cpp
+++ b/src/read_workbook.cpp
@@ -490,7 +490,7 @@ SEXP read_workbook(IntegerVector cols_in,
   if(hasColNames){
     
     int row_1 = rows[0];
-    char name[6];
+    char name[20];
     
     IntegerVector row1_inds = which_cpp(rows == row_1);
     IntegerVector header_cols = cols[row1_inds];
@@ -564,7 +564,7 @@ SEXP read_workbook(IntegerVector cols_in,
     
     
   }else{ // else col_names is FALSE
-    char name[6];
+    char name[20];
     for(int i =0; i < nCols; i++){
       sprintf(&(name[0]), "X%d", i+1);
       col_names[i] = name;