diff --git a/libsolidity/ast/Types.cpp b/libsolidity/ast/Types.cpp
index fe59e76e3..68e600055 100644
--- a/libsolidity/ast/Types.cpp
+++ b/libsolidity/ast/Types.cpp
@@ -1224,27 +1224,29 @@ FixedPointType const* RationalNumberType::fixedPointType() const
 
 pair<RationalNumberType const*, RationalNumberType const*> RationalNumberType::mantissaExponent() const
 {
-	bool negative = (m_value < 0);
-	int exponent = 0;
-	rational value = abs(m_value); // We care about the sign later.
-	rational maxValue = negative ?
-		rational(bigint(1) << 255, 1):
-		rational((bigint(1) << 256) - 1, 1);
+	rational const maxUint = rational((bigint(1) << 256) - 1);
+	rational const minInt = -rational(bigint(1) << 255);
 
-	while (value.denominator() != 1)
+	bool negative = (m_value < 0);
+	rational const maxMantissa = (negative ? -minInt : maxUint);
+
+	int exponent = 0;
+	rational unsignedMantissa = abs(m_value);
+	while (unsignedMantissa.denominator() != 1)
 	{
-		value *= 10;
-		exponent--;
+		unsignedMantissa *= 10;
+		--exponent;
+
 		if (
-			value > rational((bigint(1) << 256) - 1) ||
-			value < rational(-(bigint(1) << 255)) ||
-			exponent < -255 // TODO sane vale?
+			unsignedMantissa > maxUint ||
+			unsignedMantissa < minInt ||
+			exponent < -255 // TODO: sane value?
 		)
 			return {nullptr, nullptr};
 	}
 
 	return {
-		TypeProvider::rationalNumber(value),
+		TypeProvider::rationalNumber(unsignedMantissa),
 		TypeProvider::rationalNumber(-exponent),
 	};
 }
diff --git a/libsolidity/ast/Types.h b/libsolidity/ast/Types.h
index 78bb806f7..9b4567793 100644
--- a/libsolidity/ast/Types.h
+++ b/libsolidity/ast/Types.h
@@ -587,7 +587,12 @@ public:
 	/// @returns true if the value is not an integer.
 	bool isFractional() const { return m_value.denominator() != 1; }
 
-	/// TODO document
+	// TODO: Update if it turns out we do need to support negative numbers here.
+	/// Tries to decompose a positive rational number into two positive integers - a mantissa and a
+	/// base-10 exponent, such that the number is equal to `mantissa * 10**-exponent`.
+	/// @returns Pair of non-null pointers representing the types of the literals corresponding to
+	/// mantissa and exponent if the resulting mantissa and exponent both fit in 256 bits.
+	/// A pair of null pointers otherwise.
 	std::pair<RationalNumberType const*, RationalNumberType const*> mantissaExponent() const;
 
 	/// @returns true if the value is negative.