diff --git a/exercises/prime-factors/Example.cs b/exercises/prime-factors/Example.cs
index 91d3df31a3..d52dd89383 100644
--- a/exercises/prime-factors/Example.cs
+++ b/exercises/prime-factors/Example.cs
@@ -2,9 +2,9 @@
 
 public class PrimeFactors
 {
-    public static int[] Factors(long number)
+    public static long[] Factors(long number)
     {
-        var primes = new List<int>();
+        var primes = new List<long>();
         int divisor = 2;
         while (number > 1)
         {
diff --git a/exercises/prime-factors/PrimeFactors.cs b/exercises/prime-factors/PrimeFactors.cs
index fcb7016eb6..692a118d1e 100644
--- a/exercises/prime-factors/PrimeFactors.cs
+++ b/exercises/prime-factors/PrimeFactors.cs
@@ -2,7 +2,7 @@
 
 public static class PrimeFactors
 {
-    public static int[] Factors(long number)
+    public static long[] Factors(long number)
     {
         throw new NotImplementedException();
     }
diff --git a/exercises/prime-factors/PrimeFactorsTest.cs b/exercises/prime-factors/PrimeFactorsTest.cs
index 331329a789..a67e9c3c14 100644
--- a/exercises/prime-factors/PrimeFactorsTest.cs
+++ b/exercises/prime-factors/PrimeFactorsTest.cs
@@ -13,36 +13,36 @@ public void No_factors()
     [Fact(Skip = "Remove to run test")]
     public void Prime_number()
     {
-        Assert.Equal(new[] { 2 }, PrimeFactors.Factors(2L));
+        Assert.Equal(new[] { 2L }, PrimeFactors.Factors(2L));
     }
 
     [Fact(Skip = "Remove to run test")]
     public void Square_of_a_prime()
     {
-        Assert.Equal(new[] { 3, 3 }, PrimeFactors.Factors(9L));
+        Assert.Equal(new[] { 3L, 3L }, PrimeFactors.Factors(9L));
     }
 
     [Fact(Skip = "Remove to run test")]
     public void Cube_of_a_prime()
     {
-        Assert.Equal(new[] { 2, 2, 2 }, PrimeFactors.Factors(8L));
+        Assert.Equal(new[] { 2L, 2L, 2L }, PrimeFactors.Factors(8L));
     }
 
     [Fact(Skip = "Remove to run test")]
     public void Product_of_primes_and_non_primes()
     {
-        Assert.Equal(new[] { 2, 2, 3 }, PrimeFactors.Factors(12L));
+        Assert.Equal(new[] { 2L, 2L, 3L }, PrimeFactors.Factors(12L));
     }
 
     [Fact(Skip = "Remove to run test")]
     public void Product_of_primes()
     {
-        Assert.Equal(new[] { 5, 17, 23, 461 }, PrimeFactors.Factors(901255L));
+        Assert.Equal(new[] { 5L, 17L, 23L, 461L }, PrimeFactors.Factors(901255L));
     }
 
     [Fact(Skip = "Remove to run test")]
     public void Factors_include_a_large_prime()
     {
-        Assert.Equal(new[] { 11, 9539, 894119 }, PrimeFactors.Factors(93819012551L));
+        Assert.Equal(new[] { 11L, 9539L, 894119L }, PrimeFactors.Factors(93819012551L));
     }
 }
\ No newline at end of file
diff --git a/generators/Exercises/Generators/PrimeFactors.cs b/generators/Exercises/Generators/PrimeFactors.cs
index 09c0dad850..e157bc923a 100644
--- a/generators/Exercises/Generators/PrimeFactors.cs
+++ b/generators/Exercises/Generators/PrimeFactors.cs
@@ -1,10 +1,18 @@
-using Exercism.CSharp.Output;
+using System.Linq;
+using Exercism.CSharp.Output;
 
 namespace Exercism.CSharp.Exercises.Generators
 {
     public class PrimeFactors : GeneratorExercise
     {
-        protected override void UpdateTestMethod(TestMethod testMethod) =>
+        protected override void UpdateTestMethod(TestMethod testMethod)
+        {
             testMethod.Input["value"] = (long)testMethod.Input["value"];
+
+            if (testMethod.Expected is int[] expected)
+            {
+                testMethod.Expected = expected.Select(l => (long)l).ToArray();
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/generators/Output/TestClassOutput.cs b/generators/Output/TestClassOutput.cs
index d76cc94ef7..44b5fac2fe 100644
--- a/generators/Output/TestClassOutput.cs
+++ b/generators/Output/TestClassOutput.cs
@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.IO;
 using System.Linq;
 using Exercism.CSharp.Helpers;