diff --git a/news/1799-bugfix.md b/news/1799-bugfix.md
new file mode 100644
index 000000000..c773b31a9
--- /dev/null
+++ b/news/1799-bugfix.md
@@ -0,0 +1 @@
+Re-add a parameterless constructor to DynamicRejector so it can be loaded via reflection in CohortExtractorHost.
diff --git a/src/microservices/Microservices.CohortExtractor/Execution/RequestFulfillers/Dynamic/DynamicRejector.cs b/src/microservices/Microservices.CohortExtractor/Execution/RequestFulfillers/Dynamic/DynamicRejector.cs
index faa7e2f10..0cde6d169 100644
--- a/src/microservices/Microservices.CohortExtractor/Execution/RequestFulfillers/Dynamic/DynamicRejector.cs
+++ b/src/microservices/Microservices.CohortExtractor/Execution/RequestFulfillers/Dynamic/DynamicRejector.cs
@@ -12,11 +12,12 @@ public class DynamicRejector : IRejector
         private readonly Script<string> _script;
         private const string DefaultDynamicRulesPath = "./DynamicRules.txt";
 
+        public DynamicRejector()
+            : this(null) {}
+
         public DynamicRejector(string? dynamicRulesPath, IFileSystem? fileSystem = null)
         {
-            if (dynamicRulesPath == null)
-                dynamicRulesPath = DefaultDynamicRulesPath;
-
+            dynamicRulesPath ??= DefaultDynamicRulesPath;
             fileSystem ??= new FileSystem();
 
             if (!fileSystem.File.Exists(dynamicRulesPath))
diff --git a/tests/microservices/Microservices.CohortExtractor.Tests/Execution/RequestFulfillers/Dynamic/DynamicRejectorTests.cs b/tests/microservices/Microservices.CohortExtractor.Tests/Execution/RequestFulfillers/Dynamic/DynamicRejectorTests.cs
index 4e5491887..26a2c1bd5 100644
--- a/tests/microservices/Microservices.CohortExtractor.Tests/Execution/RequestFulfillers/Dynamic/DynamicRejectorTests.cs
+++ b/tests/microservices/Microservices.CohortExtractor.Tests/Execution/RequestFulfillers/Dynamic/DynamicRejectorTests.cs
@@ -40,5 +40,11 @@ public void Constructor_MissingRulesFile_Throws()
         Assert.Throws<FileNotFoundException>(() => new DynamicRejector("foo.txt", new MockFileSystem()));
     }
 
+    [Test]
+    public void Constructor_ExistsWithNoArgs()
+    {
+        _ = new DynamicRejector();
+    }
+
     #endregion
 }