diff --git a/UPolynomialRoots.pas b/UPolynomialRoots.pas
index 6853b80..fa1280c 100644
--- a/UPolynomialRoots.pas
+++ b/UPolynomialRoots.pas
@@ -37,6 +37,8 @@ type
 
   TIsolatingIntervals = specialize TList<TIsolatingInterval>;
 
+  TIsolatingIntervalArray = array of TIsolatingInterval;
+
   { TPolynomialRoots }
 
   TPolynomialRoots = class
@@ -48,10 +50,10 @@ type
       TIsolatingInterval;
   public
     // Returns root-isolating intervals for non-negative, non-multiple roots.
-    class function BisectIsolation(constref APolynomial: TBigIntPolynomial): TIsolatingIntervals;
+    class function BisectIsolation(constref APolynomial: TBigIntPolynomial): TIsolatingIntervalArray;
     // Returns root-isolating intervals for non-multiple roots in the interval [0, 2^boundexp].
     class function BisectIsolation(constref APolynomial: TBigIntPolynomial; constref ABoundExp: Cardinal):
-      TIsolatingIntervals;
+      TIsolatingIntervalArray;
   end;
 
 implementation
@@ -100,7 +102,7 @@ begin
   end;
 end;
 
-class function TPolynomialRoots.BisectIsolation(constref APolynomial: TBigIntPolynomial): TIsolatingIntervals;
+class function TPolynomialRoots.BisectIsolation(constref APolynomial: TBigIntPolynomial): TIsolatingIntervalArray;
 var
   boundExp: Cardinal;
 begin
@@ -111,7 +113,7 @@ end;
 // This is adapted from
 // https://en.wikipedia.org/wiki/Real-root_isolation#Bisection_method
 class function TPolynomialRoots.BisectIsolation(constref APolynomial: TBigIntPolynomial; constref ABoundExp: Cardinal):
-  TIsolatingIntervals;
+  TIsolatingIntervalArray;
 type
   TWorkItem = record
     C, K: Cardinal;
@@ -123,8 +125,9 @@ var
   stack: TWorkStack;
   n, v: Integer;
   varq: TBigIntPolynomial;
+  iso: TIsolatingIntervals;
 begin
-  Result := TIsolatingIntervals.Create;
+  iso := TIsolatingIntervals.Create;
   stack := TWorkStack.Create;
 
   item.C := 0;
@@ -141,7 +144,7 @@ begin
       // Found an integer root at 0.
       item.P := item.P.DivideByVariable;
       Dec(n);
-      Result.Add(CreateIsolatingInterval(item.C, item.K, 0, ABoundExp));
+      iso.Add(CreateIsolatingInterval(item.C, item.K, 0, ABoundExp));
     end;
 
     varq := item.P.RevertOrderOfCoefficients.TranslateVariableByOne;
@@ -149,7 +152,7 @@ begin
     if v = 1 then
     begin
       // Found isolating interval.
-      Result.Add(CreateIsolatingInterval(item.C, item.K, 1, ABoundExp));
+      iso.Add(CreateIsolatingInterval(item.C, item.K, 1, ABoundExp));
     end
     else if v > 1 then
     begin
@@ -164,6 +167,8 @@ begin
       stack.Push(item);
     end;
   end;
+  Result := iso.ToArray;
+  iso.Free;
   stack.Free;
 end;
 
diff --git a/tests/UPolynomialRootsTestCases.pas b/tests/UPolynomialRootsTestCases.pas
index cfd9e47..91c29d3 100644
--- a/tests/UPolynomialRootsTestCases.pas
+++ b/tests/UPolynomialRootsTestCases.pas
@@ -30,7 +30,7 @@ type
 
   TPolynomialRootsTestCase = class(TTestCase)
   private
-    procedure AssertBisectResult(constref AIsolatingIntervals: TIsolatingIntervals; constref AExpectedRoots:
+    procedure AssertBisectIntervals(AIsolatingIntervals: TIsolatingIntervalArray; constref AExpectedRoots:
       array of Cardinal);
   published
     procedure TestBisectNoBound;
@@ -41,18 +41,18 @@ implementation
 
 { TPolynomialRootsTestCase }
 
-procedure TPolynomialRootsTestCase.AssertBisectResult(constref AIsolatingIntervals: TIsolatingIntervals; constref
-  AExpectedRoots: array of Cardinal);
+procedure TPolynomialRootsTestCase.AssertBisectIntervals(AIsolatingIntervals: TIsolatingIntervalArray;
+  constref AExpectedRoots: array of Cardinal);
 var
   exp: Cardinal;
   found: Boolean;
   i, foundIndex: Integer;
 begin
-  AssertEquals('Unexpected number of isolating intervals.', Length(AExpectedRoots), AIsolatingIntervals.Count);
+  AssertEquals('Unexpected number of isolating intervals.', Length(AExpectedRoots), Length(AIsolatingIntervals));
   for exp in AExpectedRoots do
   begin
     found := False;
-    for i := 0 to AIsolatingIntervals.Count - 1 do
+    for i := 0 to Length(AIsolatingIntervals) - 1 do
       if (AIsolatingIntervals[i].A <= exp) and (exp <= AIsolatingIntervals[i].B) then
       begin
         found := True;
@@ -60,7 +60,7 @@ begin
         Break;
       end;
     AssertTrue('No isolating interval for expected root ' + IntToStr(exp) + ' found.', found);
-    AIsolatingIntervals.Delete(foundIndex);
+    Delete(AIsolatingIntervals, foundIndex, 1);
   end;
 end;
 
@@ -69,14 +69,13 @@ const
   expRoots: array of Cardinal = (34000, 23017, 5);
 var
   a: TBigIntPolynomial;
-  r: TIsolatingIntervals;
+  r: TIsolatingIntervalArray;
 begin
   // y = 3 * (x - 34000) * (x - 23017) * (x - 5) * (x^2 - 19) * (x + 112)
   //   = 3 * x^6 - 170730 * x^5 + 2329429920 * x^4 + 251300082690 * x^3 - 1270471872603 * x^2 + 4774763204640 * x - 24979889760000
   a := TBigIntPolynomial.Create([-24979889760000, 4774763204640, -1270471872603, 251300082690, 2329429920, -170730, 3]);
   r := TPolynomialRoots.BisectIsolation(a);
-  AssertBisectResult(r, expRoots);
-  r.Free;
+  AssertBisectIntervals(r, expRoots);
 end;
 
 procedure TPolynomialRootsTestCase.TestBisectWithBound;
@@ -84,14 +83,13 @@ const
   expRoots: array of Cardinal = (23017, 5);
 var
   a: TBigIntPolynomial;
-  r: TIsolatingIntervals;
+  r: TIsolatingIntervalArray;
 begin
   // y = 3 * (x - 34000) * (x - 23017) * (x - 5) * (x^2 - 19) * (x + 112)
   //   = 3 * x^6 - 170730 * x^5 + 2329429920 * x^4 + 251300082690 * x^3 - 1270471872603 * x^2 + 4774763204640 * x - 24979889760000
   a := TBigIntPolynomial.Create([-24979889760000, 4774763204640, -1270471872603, 251300082690, 2329429920, -170730, 3]);
   r := TPolynomialRoots.BisectIsolation(a, 15);
-  AssertBisectResult(r, expRoots);
-  r.Free;
+  AssertBisectIntervals(r, expRoots);
 end;
 
 initialization