diff --git a/lib/roo/base.rb b/lib/roo/base.rb
index 38d5c6d6..9cbd2083 100644
--- a/lib/roo/base.rb
+++ b/lib/roo/base.rb
@@ -244,7 +244,7 @@ def find(*args) # :nodoc
       [col, cell(@header_line,col)]
     end]
     #-- id
-    if args[0].class == Fixnum
+    if args[0].class == Integer
       rownum = args[0]
       if @header_line
         [Hash[1.upto(self.row().size).map {|j|
@@ -309,7 +309,7 @@ def set(row,col,value,sheet=nil) #:nodoc:
     read_cells(sheet)
     row, col = normalize(row,col)
     cell_type = case value
-                when Fixnum then :float
+                when Integer then :float
                 when String, Float then :string
                 else
                   raise ArgumentError, "Type for #{value} not set"
@@ -623,7 +623,7 @@ def set_type(row,col,type,sheet=nil)
   # converts cell coordinate to numeric values of row,col
   def normalize(row,col)
     if row.class == String
-      if col.class == Fixnum
+      if col.class == Integer
         # ('A',1):
         # ('B', 5) -> (5, 2)
         row, col = col, row
@@ -711,7 +711,7 @@ def validate_sheet!(sheet)
     case sheet
     when nil
       raise ArgumentError, "Error: sheet 'nil' not valid"
-    when Fixnum
+    when Integer
       self.sheets.fetch(sheet-1) do
         raise RangeError, "sheet index #{sheet} not found"
       end
diff --git a/lib/roo/excel.rb b/lib/roo/excel.rb
index 7652bb9b..9ece84e0 100644
--- a/lib/roo/excel.rb
+++ b/lib/roo/excel.rb
@@ -198,7 +198,7 @@ def validate_sheet!(sheet)
 
   # converts name of a sheet to index (0,1,2,..)
   def sheet_no(name)
-    return name - 1 if name.is_a?(Fixnum)
+    return name - 1 if name.is_a?(Integer)
     worksheets.each_with_index do |worksheet, index|
       return index if name == normalize_string(worksheet.name)
     end
@@ -306,7 +306,7 @@ def read_cell(row, idx)
 
     cell = read_cell_content(row, idx)
     case cell
-    when Integer, Fixnum, Bignum
+    when Integer
       value_type = :float
       value = cell.to_i
     when Float
diff --git a/lib/roo/excelx.rb b/lib/roo/excelx.rb
index 30321506..eaeb2081 100644
--- a/lib/roo/excelx.rb
+++ b/lib/roo/excelx.rb
@@ -266,7 +266,7 @@ def sheets
   # returns the sheet index by name
   # passed indexes through
   def sheet_index(sheet)
-    if sheet.is_a?(Fixnum)
+    if sheet.is_a?(Integer)
       sheet
     else
       sheets.index(sheet)
diff --git a/scripts/txt2html b/scripts/txt2html
index aac07a19..6e69ec0b 100644
--- a/scripts/txt2html
+++ b/scripts/txt2html
@@ -9,7 +9,7 @@ require File.dirname(__FILE__) + '/../lib/roo/version.rb'
 version  = Roo::VERSION::STRING
 download = 'http://rubyforge.org/projects/roo'
 
-class Fixnum
+class Integer
   def ordinal
     # teens
     return 'th' if (10..19).include?(self % 100)