diff --git a/src/Lib.hs b/src/Lib.hs
index 172cced..e244e22 100644
--- a/src/Lib.hs
+++ b/src/Lib.hs
@@ -64,13 +64,14 @@ constantInteger = try (do
 
 constantRational :: Parser Rational
 constantRational = do
-    natural <- m_natural
-    _       <- char '.'
-    decimal <- m_natural
+    natural        <- m_natural
+    _              <- char '.'
+    decimal_digits <- many digit
+    let decimal = read decimal_digits :: Integer
     let natural_length = length . show $ natural
-    let decimal_length = length . show $ decimal
+    let decimal_length = length decimal_digits
     let numerator   = natural * (10 ^ decimal_length) + decimal
-    let denominator = 10 ^ (decimal_length + natural_length - 2)
+    let denominator = 10 ^ (decimal_length + natural_length - 1)
     return (numerator % denominator)
 
 {-