diff --git a/src/NzbDrone.Common/Extensions/DictionaryExtensions.cs b/src/NzbDrone.Common/Extensions/DictionaryExtensions.cs
index db84e6139..e2b7529c3 100644
--- a/src/NzbDrone.Common/Extensions/DictionaryExtensions.cs
+++ b/src/NzbDrone.Common/Extensions/DictionaryExtensions.cs
@@ -6,11 +6,13 @@ namespace NzbDrone.Common.Extensions
 {
     public static class DictionaryExtensions
     {
-        public static TValue GetValueOrDefault<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, TValue defaultValue = default(TValue))
+#if !NETCOREAPP3_0
+        public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, TKey key, TValue defaultValue = default(TValue))
         {
             TValue value;
             return dictionary.TryGetValue(key, out value) ? value : defaultValue;
         }
+#endif
 
         public static Dictionary<T1, T2> Merge<T1, T2>(this Dictionary<T1, T2> first, Dictionary<T1, T2> second)
         {
diff --git a/src/NzbDrone.Core/Blacklisting/BlacklistService.cs b/src/NzbDrone.Core/Blacklisting/BlacklistService.cs
index e92b7f878..af71f0c0d 100644
--- a/src/NzbDrone.Core/Blacklisting/BlacklistService.cs
+++ b/src/NzbDrone.Core/Blacklisting/BlacklistService.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using NzbDrone.Common.Extensions;
 using NzbDrone.Core.Datastore;
diff --git a/src/NzbDrone.Core/CustomFormats/FormatTag.cs b/src/NzbDrone.Core/CustomFormats/FormatTag.cs
index 1aeefc359..5a0ca7b92 100644
--- a/src/NzbDrone.Core/CustomFormats/FormatTag.cs
+++ b/src/NzbDrone.Core/CustomFormats/FormatTag.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
 using System.Text.RegularExpressions;
diff --git a/src/NzbDrone.Core/Download/Clients/Deluge/Deluge.cs b/src/NzbDrone.Core/Download/Clients/Deluge/Deluge.cs
index 96b9d2bdb..a5df89276 100644
--- a/src/NzbDrone.Core/Download/Clients/Deluge/Deluge.cs
+++ b/src/NzbDrone.Core/Download/Clients/Deluge/Deluge.cs
@@ -1,23 +1,21 @@
 using System;
-using System.Linq;
 using System.Collections.Generic;
+using System.Linq;
+using System.Net;
+using FluentValidation.Results;
+using NLog;
 using NzbDrone.Common.Disk;
+using NzbDrone.Common.Extensions;
 using NzbDrone.Common.Http;
+using NzbDrone.Core.Configuration;
 using NzbDrone.Core.MediaFiles.TorrentInfo;
+using NzbDrone.Core.Organizer;
 using NzbDrone.Core.Parser.Model;
-using NzbDrone.Core.Configuration;
-using NzbDrone.Core.Validation;
-using NLog;
-using FluentValidation.Results;
-using System.Net;
 using NzbDrone.Core.RemotePathMappings;
-using NzbDrone.Core.Organizer;
+using NzbDrone.Core.Validation;
 
 namespace NzbDrone.Core.Download.Clients.Deluge
 {
-    // this is here to resolve ambiguity in GetValueOrDefault extension method in net core 3
-    using NzbDrone.Common.Extensions;
-
     public class Deluge : TorrentClientBase<DelugeSettings>
     {
         private readonly IDelugeProxy _proxy;
diff --git a/src/NzbDrone.Core/Download/Clients/Hadouken/HadoukenProxy.cs b/src/NzbDrone.Core/Download/Clients/Hadouken/HadoukenProxy.cs
index a2a706d1e..7dee6fb32 100644
--- a/src/NzbDrone.Core/Download/Clients/Hadouken/HadoukenProxy.cs
+++ b/src/NzbDrone.Core/Download/Clients/Hadouken/HadoukenProxy.cs
@@ -12,7 +12,7 @@ namespace NzbDrone.Core.Download.Clients.Hadouken
     {
         HadoukenSystemInfo GetSystemInfo(HadoukenSettings settings);
         HadoukenTorrent[] GetTorrents(HadoukenSettings settings);
-        IDictionary<string, object> GetConfig(HadoukenSettings settings);
+        IReadOnlyDictionary<string, object> GetConfig(HadoukenSettings settings);
         string AddTorrentFile(HadoukenSettings settings, byte[] fileContent);
         void AddTorrentUri(HadoukenSettings settings, string torrentUrl);
         void RemoveTorrent(HadoukenSettings settings, string downloadId);
@@ -42,9 +42,9 @@ namespace NzbDrone.Core.Download.Clients.Hadouken
             return GetTorrents(result.Torrents);
         }
 
-        public IDictionary<string, object> GetConfig(HadoukenSettings settings)
+        public IReadOnlyDictionary<string, object> GetConfig(HadoukenSettings settings)
         {
-            return ProcessRequest<IDictionary<string, object>>(settings, "webui.getSettings");
+            return ProcessRequest<IReadOnlyDictionary<string, object>>(settings, "webui.getSettings");
         }
 
         public string AddTorrentFile(HadoukenSettings settings, byte[] fileContent)
diff --git a/src/NzbDrone.Core/Download/Clients/Nzbget/Nzbget.cs b/src/NzbDrone.Core/Download/Clients/Nzbget/Nzbget.cs
index c7429f814..ad9a496aa 100644
--- a/src/NzbDrone.Core/Download/Clients/Nzbget/Nzbget.cs
+++ b/src/NzbDrone.Core/Download/Clients/Nzbget/Nzbget.cs
@@ -6,6 +6,7 @@ using System.Linq;
 using FluentValidation.Results;
 using NLog;
 using NzbDrone.Common.Disk;
+using NzbDrone.Common.Extensions;
 using NzbDrone.Common.Http;
 using NzbDrone.Core.Configuration;
 using NzbDrone.Core.Exceptions;
@@ -16,9 +17,6 @@ using NzbDrone.Core.Organizer;
 
 namespace NzbDrone.Core.Download.Clients.Nzbget
 {
-    // this is here to resolve ambiguity in GetValueOrDefault extension method in net core 3
-    using NzbDrone.Common.Extensions;
-
     public class Nzbget : UsenetClientBase<NzbgetSettings>
     {
         private readonly INzbgetProxy _proxy;
diff --git a/src/NzbDrone.Core/Organizer/FileNameBuilder.cs b/src/NzbDrone.Core/Organizer/FileNameBuilder.cs
index 562536001..ff3afd934 100644
--- a/src/NzbDrone.Core/Organizer/FileNameBuilder.cs
+++ b/src/NzbDrone.Core/Organizer/FileNameBuilder.cs
@@ -311,7 +311,7 @@ namespace NzbDrone.Core.Organizer
         }
 
         private const string MediaInfoVideoDynamicRangeToken = "{MediaInfo VideoDynamicRange}";
-        private static readonly IDictionary<string, int> MinimumMediaInfoSchemaRevisions =
+        private static readonly IReadOnlyDictionary<string, int> MinimumMediaInfoSchemaRevisions =
             new Dictionary<string, int>(FileNameBuilderTokenEqualityComparer.Instance)
         {
             {MediaInfoVideoDynamicRangeToken, 5}
diff --git a/src/NzbDrone.Core/Parser/Model/ParsedMovieInfo.cs b/src/NzbDrone.Core/Parser/Model/ParsedMovieInfo.cs
index bbcd0989e..f1be1499f 100644
--- a/src/NzbDrone.Core/Parser/Model/ParsedMovieInfo.cs
+++ b/src/NzbDrone.Core/Parser/Model/ParsedMovieInfo.cs
@@ -27,7 +27,7 @@ namespace NzbDrone.Core.Parser.Model
         /// It is expanded by the augmenters.
         /// </summary>
         [JsonIgnore]
-        public IDictionary<string, object> ExtraInfo = new Dictionary<string, object>();
+        public Dictionary<string, object> ExtraInfo = new Dictionary<string, object>();
         public List<Language> Languages = new List<Language>();
         public string ReleaseGroup { get; set; }
         public string ReleaseHash { get; set; }
diff --git a/src/NzbDrone.Mono/Disk/ProcMountProvider.cs b/src/NzbDrone.Mono/Disk/ProcMountProvider.cs
index 3f456b499..88e834d8a 100644
--- a/src/NzbDrone.Mono/Disk/ProcMountProvider.cs
+++ b/src/NzbDrone.Mono/Disk/ProcMountProvider.cs
@@ -5,12 +5,10 @@ using System.Linq;
 using System.Text.RegularExpressions;
 using NLog;
 using NzbDrone.Common.Disk;
+using NzbDrone.Common.Extensions;
 
 namespace NzbDrone.Mono.Disk
 {
-    // this is here to resolve ambiguity in GetValueOrDefault extension method in net core 3
-    using NzbDrone.Common.Extensions;
-
     public interface IProcMountProvider
     {
         List<IMount> GetMounts();
diff --git a/src/Radarr.Http/Extensions/Pipelines/GZipPipeline.cs b/src/Radarr.Http/Extensions/Pipelines/GZipPipeline.cs
index e2ff93cff..3d8804195 100644
--- a/src/Radarr.Http/Extensions/Pipelines/GZipPipeline.cs
+++ b/src/Radarr.Http/Extensions/Pipelines/GZipPipeline.cs
@@ -6,7 +6,6 @@ using Nancy;
 using Nancy.Bootstrapper;
 using NLog;
 using NzbDrone.Common.EnvironmentInfo;
-using NzbDrone.Common.Extensions;
 
 namespace Radarr.Http.Extensions.Pipelines
 {
@@ -81,7 +80,7 @@ namespace Radarr.Http.Extensions.Pipelines
 
         private static bool ContentLengthIsTooSmall(Response response)
         {
-            var contentLength = response.Headers.GetValueOrDefault("Content-Length");
+            var contentLength = response.Headers.TryGetValue("Content-Length", out var value) ? value : null;
 
             if (contentLength != null && long.Parse(contentLength) < 1024)
             {
@@ -93,7 +92,7 @@ namespace Radarr.Http.Extensions.Pipelines
 
         private static bool AlreadyGzipEncoded(Response response)
         {
-            var contentEncoding = response.Headers.GetValueOrDefault("Content-Encoding");
+            var contentEncoding = response.Headers.TryGetValue("Content-Encoding", out var value) ? value : null;
 
             if (contentEncoding == "gzip")
             {