diff --git a/src/Geta.404Handler/Core/CustomRedirects/CustomRedirectCollection.cs b/src/Geta.404Handler/Core/CustomRedirects/CustomRedirectCollection.cs
index 2be62a3..66a5ba1 100644
--- a/src/Geta.404Handler/Core/CustomRedirects/CustomRedirectCollection.cs
+++ b/src/Geta.404Handler/Core/CustomRedirects/CustomRedirectCollection.cs
@@ -144,7 +144,7 @@ string RemoveSlash(string s)
             }
 
             var redirCopy = new CustomRedirect(cr);
-            var newUrl = AppendSlash(redirCopy.NewUrl);
+            var newUrl = url.IndexOf("?", StringComparison.Ordinal) > 0 ? redirCopy.NewUrl : AppendSlash(redirCopy.NewUrl);
             var appendSegment = RemoveSlash(url.Substring(oldUrl.Length));
             redirCopy.NewUrl = $"{newUrl}{appendSegment}";
             return redirCopy;
diff --git a/tests/Geta.404Handler.Tests/CustomRedirectCollectionTests.cs b/tests/Geta.404Handler.Tests/CustomRedirectCollectionTests.cs
index c124919..be6cb04 100644
--- a/tests/Geta.404Handler.Tests/CustomRedirectCollectionTests.cs
+++ b/tests/Geta.404Handler.Tests/CustomRedirectCollectionTests.cs
@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Web;
 using BVNetwork.NotFound.Core;
@@ -276,5 +276,65 @@ public void Find_gives_nullreferenceexception_with_partial_deleted_hit()
 
             Assert.NotNull(actual);
         }
+
+        /// <summary>
+        /// https://github.com/Geta/404handler/issues/171
+        /// </summary>
+        [Fact]
+        public void Find_does_not_add_slash_when_querystring_parameter()
+        {
+            var collection = new CustomRedirectCollection
+            {
+                new CustomRedirect("/content/file", "/legacy"),
+                new CustomRedirect("/content/file/", "/legacy/")
+            };
+
+            var urlToFind = "/content/file?doc=filename";
+            var expected = "/legacy?doc=filename";
+
+            var actual = collection.Find(urlToFind.ToUri());
+
+            Assert.Equal(expected, actual.NewUrl);
+        }
+
+        /// <summary>
+        /// https://github.com/Geta/404handler/issues/171
+        /// </summary>
+        [Fact]
+        public void Find_does_keep_slash_when_querystring_parameter()
+        {
+            var collection = new CustomRedirectCollection
+            {
+                new CustomRedirect("/content/file", "/legacy"),
+                new CustomRedirect("/content/file/", "/legacy/")
+            };
+
+            var urlToFind = "/content/file/?doc=filename";
+            var expected = "/legacy/?doc=filename";
+
+            var actual = collection.Find(urlToFind.ToUri());
+
+            Assert.Equal(expected, actual.NewUrl);
+        }
+
+        /// <summary>
+        /// https://github.com/Geta/404handler/issues/171
+        /// </summary>
+        [Fact]
+        public void Find_does_not_add_slash_when_querystring_parameters()
+        {
+            var collection = new CustomRedirectCollection
+            {
+                new CustomRedirect("/content/file", "/legacy"),
+                new CustomRedirect("/content/file/", "/legacy/")
+            };
+
+            var urlToFind = "/content/file?doc=filename&param2=value";
+            var expected = "/legacy?doc=filename&param2=value";
+
+            var actual = collection.Find(urlToFind.ToUri());
+
+            Assert.Equal(expected, actual.NewUrl);
+        }
     }
-}
\ No newline at end of file
+}