diff --git a/src/Toml/Parser/Core.hs b/src/Toml/Parser/Core.hs
index 02589ddc..1d8cc51c 100644
--- a/src/Toml/Parser/Core.hs
+++ b/src/Toml/Parser/Core.hs
@@ -26,7 +26,7 @@ import Data.Void (Void)
 
 import Text.Megaparsec (Parsec, anySingle, eof, errorBundlePretty, match, parse, satisfy, try,
                         (<?>))
-import Text.Megaparsec.Char (alphaNumChar, char, digitChar, eol, hexDigitChar, space, space1,
+import Text.Megaparsec.Char (alphaNumChar, char, digitChar, eol, hexDigitChar, octDigitChar, binDigitChar, space, space1,
                              string, tab)
 import Text.Megaparsec.Char.Lexer (binary, float, hexadecimal, octal, signed, skipLineComment,
                                    symbol)
diff --git a/src/Toml/Parser/Value.hs b/src/Toml/Parser/Value.hs
index f76985ef..901d9694 100644
--- a/src/Toml/Parser/Value.hs
+++ b/src/Toml/Parser/Value.hs
@@ -22,9 +22,12 @@ import Control.Applicative.Combinators (between, count, option, optional, sepBy1
 import Data.Fixed (Pico)
 import Data.Time (Day, LocalTime (..), TimeOfDay, ZonedTime (..), fromGregorianValid,
                   makeTimeOfDayValid, minutesToTimeZone)
+import Data.String (fromString)
+
 import Text.Read (readMaybe)
+import Text.Megaparsec (parseMaybe)
 
-import Toml.Parser.Core (Parser, binary, char, digitChar, hexadecimal, lexeme, octal, sc, signed,
+import Toml.Parser.Core (Parser, char, digitChar, hexDigitChar, octDigitChar, binDigitChar, hexadecimal, octal, binary, lexeme, sc, signed,
                          string, text, try, (<?>))
 import Toml.Parser.String (textP)
 import Toml.Type (AnyValue, UValue (..), typeCheck)
@@ -41,15 +44,33 @@ decimalP = zero <|> more
     check :: Maybe Integer -> Parser Integer
     check = maybe (fail "Not an integer") pure
 
+-- | Parser for hexadecimal, octal and binary numbers : included parsing
+numberP :: Parser Integer -> Parser Char -> String -> Parser Integer
+numberP parseInteger parseDigit errorMessage = more
+  where
+    more :: Parser Integer
+    more = check =<< intValueMaybe . concat <$> sepBy1 (some parseDigit) (char '_')
+
+    intValueMaybe :: String -> Maybe Integer
+    intValueMaybe = parseMaybe parseInteger . fromString
+
+    check :: Maybe Integer -> Parser Integer
+    check = maybe (fail errorMessage) pure
+
+
+
 -- | Parser for 'Integer' value.
 integerP :: Parser Integer
 integerP = lexeme (bin <|> oct <|> hex <|> dec) <?> "integer"
   where
     bin, oct, hex, dec :: Parser Integer
-    bin = try (char '0' *> char 'b') *> binary      <?> "bin"
-    oct = try (char '0' *> char 'o') *> octal       <?> "oct"
-    hex = try (char '0' *> char 'x') *> hexadecimal <?> "hex"
+    bin = try (char '0' *> char 'b') *> binaryP      <?> "bin"
+    oct = try (char '0' *> char 'o') *> octalP       <?> "oct"
+    hex = try (char '0' *> char 'x') *> hexadecimalP <?> "hex"
     dec = signed sc decimalP                        <?> "dec"
+    binaryP = numberP binary binDigitChar "Invalid binary number"
+    octalP  = numberP octal octDigitChar  "Invalid ocatl number"
+    hexadecimalP = numberP hexadecimal hexDigitChar "Invalid hexadecimal number"
 
 -- | Parser for 'Double' value.
 doubleP :: Parser Double
diff --git a/test/Test/Toml/Parser/Integer.hs b/test/Test/Toml/Parser/Integer.hs
index 3bc6a678..ad300145 100644
--- a/test/Test/Toml/Parser/Integer.hs
+++ b/test/Test/Toml/Parser/Integer.hs
@@ -81,3 +81,41 @@ integerSpecs = describe "integerP" $ do
         it "can parse numbers when hex digits are in both lowercase and uppercase" $ do
             parseInteger "0xAbCdEf" 0xAbCdEf
             parseInteger "0xaBcDeF" 0xaBcDeF
+    context "when there is underscore in hexadecimal, octal and binary representation" $ do
+        it "can parse numbers with underscore in hexadecimal representation" $ do
+            parseInteger "0xAb_Cd_Ef" 0xabcdef
+            parseInteger "0xA_bcd_ef" 0xabcdef
+            parseInteger "0x123_abc" 0x123abc
+            parseInteger "0xa_b_c_1_2_3" 0xabc123
+        it "can't parse when underscore is between hexadecimal prefix and suffix" $ do
+            integerFailOn "0x_Abab_ca"
+            integerFailOn "0x_ababbac"
+        it "can parse numbers with underscore in octal representation" $ do
+            parseInteger "0o12_34_56" 0o123456
+            parseInteger "0o1_2345_6" 0o123456
+            parseInteger "0o76_54_21" 0o765421
+            parseInteger "0o4_5_3_2_6" 0o45326
+        it "can't parse when underscore is between octal prefix and suffix" $ do
+            integerFailOn "0o_123_4567"
+            integerFailOn "0o_1234567"
+        it "can parse numbers with underscore in binary representation" $ do
+            parseInteger "0b10_101_0" 42
+            parseInteger "0b10_10_10" 42
+            parseInteger "0b1_0_1" 5
+            parseInteger "0b1_0" 2
+        it "can't parse numbers when underscore is between binary prefix and suffix" $ do
+            integerFailOn "0b_10101_0"
+            integerFailOn "0b_101010"
+        it "doesn't parse underscore not followed by any numbers" $ do 
+            integerFailOn "0b_"
+            integerFailOn "0o_"
+            integerFailOn "0x_"
+        it "doesn't parse when number is ending with underscore" $ do 
+            integerFailOn "0b101_110_"
+            integerFailOn "0b10101_"
+            integerFailOn "0x1_23_daf_"
+            integerFailOn "0x1214adf_"
+            integerFailOn "0o1_15_41_"
+            integerFailOn "0o1215147_"
+            
+