diff --git a/CHANGELOG.md b/CHANGELOG.md
index aef9f2a1..2a04f0d1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ changes you may need to make.
 
 - API Key is now sent via the `X-Api-Key` header instead of the `apikey` query parameter. This
   lessens the need to redact information in the console.
+- **BREAKING**: `replace_existing_custom_formats` now defaults to `true`
 
 ### Removed
 
diff --git a/src/Recyclarr.TrashLib.Tests/Config/Parsing/ConfigurationLoaderTest.cs b/src/Recyclarr.TrashLib.Tests/Config/Parsing/ConfigurationLoaderTest.cs
index 88a8efb1..c848d760 100644
--- a/src/Recyclarr.TrashLib.Tests/Config/Parsing/ConfigurationLoaderTest.cs
+++ b/src/Recyclarr.TrashLib.Tests/Config/Parsing/ConfigurationLoaderTest.cs
@@ -94,7 +94,7 @@ public class ConfigurationLoaderTest : TrashLibIntegrationFixture
                     ApiKey = "95283e6b156c42f3af8a9b16173f876b",
                     BaseUrl = new Uri("http://localhost:8989"),
                     InstanceName = "name",
-                    ReplaceExistingCustomFormats = true,
+                    ReplaceExistingCustomFormats = false,
                     ReleaseProfiles = new List<ReleaseProfileConfig>
                     {
                         new()
diff --git a/src/Recyclarr.TrashLib/Config/Parsing/ConfigYamlDataObjects.cs b/src/Recyclarr.TrashLib/Config/Parsing/ConfigYamlDataObjects.cs
index 8cd4f805..bf7ff2e4 100644
--- a/src/Recyclarr.TrashLib/Config/Parsing/ConfigYamlDataObjects.cs
+++ b/src/Recyclarr.TrashLib/Config/Parsing/ConfigYamlDataObjects.cs
@@ -34,9 +34,7 @@ public record ServiceConfigYaml
     public string? BaseUrl { get; [UsedImplicitly] init; }
     public string? ApiKey { get; [UsedImplicitly] init; }
     public bool DeleteOldCustomFormats { get; [UsedImplicitly] init; }
-
-    // todo: In v5.0, this will change to false.
-    public bool ReplaceExistingCustomFormats { get; [UsedImplicitly] init; } = true;
+    public bool ReplaceExistingCustomFormats { get; [UsedImplicitly] init; }
 
     public IReadOnlyCollection<CustomFormatConfigYaml>? CustomFormats { get; [UsedImplicitly] init; }
     public QualitySizeConfigYaml? QualityDefinition { get; [UsedImplicitly] init; }
diff --git a/src/Recyclarr.TrashLib/Config/Services/IServiceConfiguration.cs b/src/Recyclarr.TrashLib/Config/Services/IServiceConfiguration.cs
index 247eb79d..d150f121 100644
--- a/src/Recyclarr.TrashLib/Config/Services/IServiceConfiguration.cs
+++ b/src/Recyclarr.TrashLib/Config/Services/IServiceConfiguration.cs
@@ -11,5 +11,5 @@ public interface IServiceConfiguration
     QualityDefinitionConfig? QualityDefinition { get; }
 
     IReadOnlyCollection<QualityProfileConfig> QualityProfiles { get; }
-    bool ReplaceExistingCustomFormats { get; init; }
+    bool ReplaceExistingCustomFormats { get; }
 }