diff --git a/Scripts/Node.cs b/Scripts/Node.cs
index cd86b95..27e32c7 100644
--- a/Scripts/Node.cs
+++ b/Scripts/Node.cs
@@ -290,16 +290,26 @@ namespace XNode {
             [Obsolete("Use dynamicPortList instead")]
             public bool instancePortList { get { return dynamicPortList; } set { dynamicPortList = value; } }
             public bool dynamicPortList;
+            public TypeConstraint typeConstraint;
+
+            /// <summary> Mark a serializable field as an output port. You can access this through <see cref="GetOutputPort(string)"/> </summary>
+            /// <param name="backingValue">Should we display the backing value for this port as an editor field? </param>
+            /// <param name="connectionType">Should we allow multiple connections? </param>
+            /// <param name="typeConstraint">Constrains which input connections can be made from this port </param>
+            /// <param name="dynamicPortList">If true, will display a reorderable list of outputs instead of a single port. Will automatically add and display values for lists and arrays </param>
+            public OutputAttribute(ShowBackingValue backingValue = ShowBackingValue.Never, ConnectionType connectionType = ConnectionType.Multiple, TypeConstraint typeConstraint = TypeConstraint.None, bool dynamicPortList = false) {
+                this.backingValue = backingValue;
+                this.connectionType = connectionType;
+                this.dynamicPortList = dynamicPortList;
+                this.typeConstraint = typeConstraint;
+            }
 
             /// <summary> Mark a serializable field as an output port. You can access this through <see cref="GetOutputPort(string)"/> </summary>
             /// <param name="backingValue">Should we display the backing value for this port as an editor field? </param>
             /// <param name="connectionType">Should we allow multiple connections? </param>
             /// <param name="dynamicPortList">If true, will display a reorderable list of outputs instead of a single port. Will automatically add and display values for lists and arrays </param>
-            public OutputAttribute(ShowBackingValue backingValue = ShowBackingValue.Never, ConnectionType connectionType = ConnectionType.Multiple, bool dynamicPortList = false) {
-                this.backingValue = backingValue;
-                this.connectionType = connectionType;
-                this.dynamicPortList = dynamicPortList;
-            }
+            [Obsolete("Use constructor with TypeConstraint")]
+            public OutputAttribute(ShowBackingValue backingValue, ConnectionType connectionType, bool dynamicPortList) : this(backingValue, connectionType, TypeConstraint.None, dynamicPortList) { }
         }
 
         [AttributeUsage(AttributeTargets.Class, AllowMultiple = false)]
diff --git a/Scripts/NodePort.cs b/Scripts/NodePort.cs
index 24e4941..1000b23 100644
--- a/Scripts/NodePort.cs
+++ b/Scripts/NodePort.cs
@@ -67,6 +67,7 @@ namespace XNode {
                 } else if (attribs[i] is Node.OutputAttribute) {
                     _direction = IO.Output;
                     _connectionType = (attribs[i] as Node.OutputAttribute).connectionType;
+                    _typeConstraint = (attribs[i] as Node.OutputAttribute).typeConstraint;
                 }
             }
         }
@@ -255,9 +256,12 @@ namespace XNode {
             else output = port;
             // If there isn't one of each, they can't connect
             if (input == null || output == null) return false;
-            // Check type constraints
+            // Check input type constraints
             if (input.typeConstraint == XNode.Node.TypeConstraint.Inherited && !input.ValueType.IsAssignableFrom(output.ValueType)) return false;
             if (input.typeConstraint == XNode.Node.TypeConstraint.Strict && input.ValueType != output.ValueType) return false;
+            // Check output type constraints
+            if (output.typeConstraint == XNode.Node.TypeConstraint.Inherited && !output.ValueType.IsAssignableFrom(input.ValueType)) return false;
+            if (output.typeConstraint == XNode.Node.TypeConstraint.Strict && output.ValueType != input.ValueType) return false;
             // Success
             return true;
         }