diff --git a/packages/cpp/src/ConstantProductPool.ts b/packages/cpp/src/ConstantProductPool.ts
index a13f6b3..1f5b1d2 100644
--- a/packages/cpp/src/ConstantProductPool.ts
+++ b/packages/cpp/src/ConstantProductPool.ts
@@ -190,8 +190,8 @@ export const getSwapOutput = (
     throw new Error("Input and reserves must be positive");
 
   fee = Fraction.asFraction(fee);
-  if (fee.lt(Fraction.ZERO) || fee.gte(Fraction.ONE))
-    throw new Error("fee must be [0,1)");
+  if (fee.lt(Fraction.ZERO) || fee.gt(Fraction.ONE))
+    throw new Error("fee must be between 0 and 1");
 
   const feeDiff = fee.denominator - fee.numerator;
   const outputNumerator = outputReserve * input * feeDiff;
diff --git a/packages/cpp/src/__tests__/ConstantProductPool.test.ts b/packages/cpp/src/__tests__/ConstantProductPool.test.ts
index 20d5440..6800fdb 100644
--- a/packages/cpp/src/__tests__/ConstantProductPool.test.ts
+++ b/packages/cpp/src/__tests__/ConstantProductPool.test.ts
@@ -28,7 +28,9 @@ describe("getSwapOutput", () => {
   });
 
   test("throws if fee is greater than or equal 1", () => {
-    expect(() => getSwapOutput(1n, 10n, 10n, Fraction.asFraction(1))).toThrow();
+    expect(() =>
+      getSwapOutput(1n, 10n, 10n, Fraction.asFraction(1)),
+    ).not.toThrow();
     expect(() =>
       getSwapOutput(1n, 10n, 10n, Fraction.asFraction(1.132)),
     ).toThrow();