diff --git a/UPolynomialRoots.pas b/UPolynomialRoots.pas
index a05c9fa..a8c13b1 100644
--- a/UPolynomialRoots.pas
+++ b/UPolynomialRoots.pas
@@ -31,7 +31,8 @@ type
   // Represents an isolating interval of the form [C / 2^K, (C + H) / 2^K] in respect to [0, 1] or [A, B] in respect to
   // [0, 2^boundexp], with A = C * 2^boundexp / 2^K and B = (C + H) * 2^boundexp / 2^K.
   TIsolatingInterval = record
-    C, K, H, BoundExp: Cardinal;
+    C: TBigInt;
+    K, H, BoundExp: Cardinal;
     A, B: TBigInt;
   end;
 
@@ -46,7 +47,7 @@ type
     // Returns the exponent (base two) of an upper bound for the roots of the given polynomial, i.e. all real roots of
     // the given polynomial are less or equal than 2^b, where b is the returned positive integer.
     class function CalcUpperRootBound(constref APolynomial: TBigIntPolynomial): Cardinal;
-    class function CreateIsolatingInterval(const AC, AK, AH: Cardinal; constref ABoundExp: Cardinal):
+    class function CreateIsolatingInterval(constref AC: TBigInt; const AK, AH: Cardinal; constref ABoundExp: Cardinal):
       TIsolatingInterval;
   public
     // Returns root-isolating intervals for non-negative, non-multiple roots.
@@ -87,8 +88,8 @@ begin
   Result := numeratorBit - denominatorBit;
 end;
 
-class function TPolynomialRoots.CreateIsolatingInterval(const AC, AK, AH: Cardinal; constref ABoundExp: Cardinal):
-  TIsolatingInterval;
+class function TPolynomialRoots.CreateIsolatingInterval(constref AC: TBigInt; const AK, AH: Cardinal;
+  constref ABoundExp: Cardinal): TIsolatingInterval;
 begin
   Result.C := AC;
   Result.K := AK;
@@ -119,7 +120,8 @@ class function TPolynomialRoots.BisectIsolation(constref APolynomial: TBigIntPol
   const AFindIntegers: Boolean): TIsolatingIntervalArray;
 type
   TWorkItem = record
-    C, K: Cardinal;
+    C: TBigInt;
+    K: Cardinal;
     P: TBigIntPolynomial;
   end;
   TWorkStack = specialize TStack<TWorkItem>;