diff --git a/Sources/KituraContracts/Contracts.swift b/Sources/KituraContracts/Contracts.swift
index fd0b12d..067fce4 100644
--- a/Sources/KituraContracts/Contracts.swift
+++ b/Sources/KituraContracts/Contracts.swift
@@ -1242,6 +1242,15 @@ public struct GreaterThan<I: Identifier>: Operation {
   private var value: I
   private let `operator`: Operator = .greaterThan
 
+  private enum CodingKeys: CodingKey {
+    case value
+  }
+
+  public init(from decoder: Decoder) throws {
+    let container = try decoder.container(keyedBy: CodingKeys.self)
+    value = try container.decode(I.self, forKey: .value)
+  }
+
   /// Creates a GreaterThan instance from a given Identifier value
   public init(value: I) {
     self.value = value
@@ -1289,6 +1298,15 @@ public struct GreaterThanOrEqual<I: Identifier>: Operation {
   private var value: I
   private let `operator`: Operator = .greaterThanOrEqual
 
+  private enum CodingKeys: CodingKey {
+    case value
+  }
+
+  public init(from decoder: Decoder) throws {
+    let container = try decoder.container(keyedBy: CodingKeys.self)
+    value = try container.decode(I.self, forKey: .value)
+  }
+
   /// Creates a GreaterThanOrEqual instance from a given Identifier value
   public init(value: I) {
     self.value = value
@@ -1337,6 +1355,15 @@ public struct LowerThan<I: Identifier>: Operation {
   private var value: I
   private let `operator`: Operator = .lowerThan
 
+  private enum CodingKeys: CodingKey {
+    case value
+  }
+
+  public init(from decoder: Decoder) throws {
+    let container = try decoder.container(keyedBy: CodingKeys.self)
+    value = try container.decode(I.self, forKey: .value)
+  }
+
   /// Creates a LowerThan instance from a given Identifier value
   public init(value: I) {
     self.value = value
@@ -1384,6 +1411,15 @@ public struct LowerThanOrEqual<I: Identifier>: Operation {
   private var value: I
   private let `operator`: Operator = .lowerThanOrEqual
 
+  private enum CodingKeys: CodingKey {
+    case value
+  }
+
+  public init(from decoder: Decoder) throws {
+    let container = try decoder.container(keyedBy: CodingKeys.self)
+    value = try container.decode(I.self, forKey: .value)
+  }
+
   /// Creates a LowerThan instance from a given Identifier value
   public init(value: I) {
     self.value = value
@@ -1432,6 +1468,17 @@ public struct InclusiveRange<I: Identifier>: Operation {
   private var end: I
   private let `operator`: Operator = .inclusiveRange
 
+  private enum CodingKeys: CodingKey {
+    case start
+    case end
+  }
+
+  public init(from decoder: Decoder) throws {
+    let container = try decoder.container(keyedBy: CodingKeys.self)
+    start = try container.decode(I.self, forKey: .start)
+    end = try container.decode(I.self, forKey: .end)
+  }
+
   /// Creates a InclusiveRange instance from given start and end values
   public init(start: I, end: I) {
     self.start = start
@@ -1486,6 +1533,17 @@ public struct ExclusiveRange<I: Identifier>: Operation {
   private var end: I
   private let `operator`: Operator = .exclusiveRange
 
+  private enum CodingKeys: CodingKey {
+    case start
+    case end
+  }
+
+  public init(from decoder: Decoder) throws {
+    let container = try decoder.container(keyedBy: CodingKeys.self)
+    start = try container.decode(I.self, forKey: .start)
+    end = try container.decode(I.self, forKey: .end)
+  }
+
   /// Creates a ExclusiveRange instance from given start and end values
   public init(start: I, end: I) {
     self.start = start