diff --git a/src/JsonApiDotNetCore/Configuration/JsonApiOptions.cs b/src/JsonApiDotNetCore/Configuration/JsonApiOptions.cs
index 2e24d52d53..3d169998a3 100644
--- a/src/JsonApiDotNetCore/Configuration/JsonApiOptions.cs
+++ b/src/JsonApiDotNetCore/Configuration/JsonApiOptions.cs
@@ -15,6 +15,15 @@ public class JsonApiOptions
         public bool AllowClientGeneratedIds { get; set; }
         public IContextGraph ContextGraph { get; set; }
         public bool RelativeLinks { get; set; }
+
+        /// <summary>
+        /// This flag is experimental and could be perceived as a violation
+        /// of the v1 spec. However, we have decided that this is a real
+        /// requirement for users of this library and a gap in the specification.
+        /// It will likely be removed when the spec is updated to support this
+        /// requirement. 
+        /// </summary>
+        public bool AllowCustomQueryParameters { get; set; }
         public IContractResolver JsonContractResolver { get; set; } = new DasherizedResolver();
         internal IContextGraphBuilder ContextGraphBuilder { get; } = new ContextGraphBuilder();
 
diff --git a/src/JsonApiDotNetCore/Internal/Query/QuerySet.cs b/src/JsonApiDotNetCore/Internal/Query/QuerySet.cs
index acf448d69d..628e6187a3 100644
--- a/src/JsonApiDotNetCore/Internal/Query/QuerySet.cs
+++ b/src/JsonApiDotNetCore/Internal/Query/QuerySet.cs
@@ -68,7 +68,8 @@ private void BuildQuerySet(IQueryCollection query)
                     continue;
                 }
 
-                throw new JsonApiException(400, $"{pair} is not a valid query.");
+                if (_jsonApiContext.Options.AllowCustomQueryParameters == false)
+                    throw new JsonApiException(400, $"{pair} is not a valid query.");
             }
         }
 
@@ -101,9 +102,9 @@ private List<FilterQuery> ParseFilterQuery(string key, string value)
                 return (string.Empty, value);
 
             // remove prefix from value
-            if(Enum.TryParse(operation[0], out FilterOperations op) == false)
+            if (Enum.TryParse(operation[0], out FilterOperations op) == false)
                 return (string.Empty, value);
-            
+
             var prefix = operation[0];
             value = string.Join(":", operation.Skip(1));
 
diff --git a/src/JsonApiDotNetCore/JsonApiDotNetCore.csproj b/src/JsonApiDotNetCore/JsonApiDotNetCore.csproj
index baad778f59..9177566e00 100755
--- a/src/JsonApiDotNetCore/JsonApiDotNetCore.csproj
+++ b/src/JsonApiDotNetCore/JsonApiDotNetCore.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <VersionPrefix>2.1.5</VersionPrefix>
+    <VersionPrefix>2.1.6</VersionPrefix>
     <TargetFrameworks>netstandard1.6</TargetFrameworks>
     <AssemblyName>JsonApiDotNetCore</AssemblyName>
     <PackageId>JsonApiDotNetCore</PackageId>
diff --git a/src/JsonApiDotNetCore/Services/QueryAccessor.cs b/src/JsonApiDotNetCore/Services/QueryAccessor.cs
index 0862e3fd3e..09942d4031 100644
--- a/src/JsonApiDotNetCore/Services/QueryAccessor.cs
+++ b/src/JsonApiDotNetCore/Services/QueryAccessor.cs
@@ -63,7 +63,7 @@ public bool TryGetValue<T>(string key, out T value)
 
         private string GetFilterValue(string key) => _jsonApiContext.QuerySet
             .Filters
-            .FirstOrDefault(f => f.Key == key)
+            .FirstOrDefault(f => string.Equals(f.Key, key, StringComparison.OrdinalIgnoreCase))
             ?.Value;
     }
 }
\ No newline at end of file