diff --git a/CUETools.Processor/CUEToolsUDC.cs b/CUETools.Processor/CUEToolsUDC.cs
index 444f7e1..42a8d27 100644
--- a/CUETools.Processor/CUEToolsUDC.cs
+++ b/CUETools.Processor/CUEToolsUDC.cs
@@ -132,11 +132,17 @@ namespace CUETools.Processor
             get { return lossless; }
             set { lossless = value; if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("Lossless")); }
         }
-        
+
         public string Extension
         {
             get { return extension; }
-            set { if (extension == value) return; extension = value; if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("Extension")); }
+            set
+            {
+                if (extension == value) return;
+                if (type != null && type != typeof(UserDefinedWriter)) throw new InvalidOperationException();
+                extension = value; 
+                if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("Extension"));
+            }
         }
         
         public string DotExtension
diff --git a/CUETools/frmCUETools.cs b/CUETools/frmCUETools.cs
index aa9d1bd..6381a62 100644
--- a/CUETools/frmCUETools.cs
+++ b/CUETools/frmCUETools.cs
@@ -2718,7 +2718,6 @@ namespace JDP
                 settingsForm.Config = _profile._config;
                 settingsForm.ShowDialog(this);
             }
-            SaveSettings();
             SelectedOutputAudioType = SelectedOutputAudioType;
         }
     }
diff --git a/CUETools/frmSettings.Designer.cs b/CUETools/frmSettings.Designer.cs
index 09f5a80..87c4e3e 100644
--- a/CUETools/frmSettings.Designer.cs
+++ b/CUETools/frmSettings.Designer.cs
@@ -1174,7 +1174,6 @@ namespace JDP
             this.comboBoxEncoderExtension.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDownList;
             this.comboBoxEncoderExtension.FormattingEnabled = true;
             this.comboBoxEncoderExtension.Name = "comboBoxEncoderExtension";
-            this.comboBoxEncoderExtension.SelectedIndexChanged += new System.EventHandler(this.comboBoxEncoderExtension_SelectedIndexChanged);
             // 
             // listBoxEncoders
             // 
diff --git a/CUETools/frmSettings.cs b/CUETools/frmSettings.cs
index 951c97e..f532e55 100644
--- a/CUETools/frmSettings.cs
+++ b/CUETools/frmSettings.cs
@@ -459,13 +459,6 @@ namespace JDP
 			}			
 		}
 
-		private void comboBoxEncoderExtension_SelectedIndexChanged(object sender, EventArgs e)
-		{
-			// Setting DataSourceUpdateMode to OnPropertyChanged doesn't seem 
-			// to do the trick, so updating manually
-			comboBoxEncoderExtension.DataBindings["SelectedItem"].WriteValue();
-		}
-
 		private void encodersBindingSource_CurrentItemChanged(object sender, EventArgs e)
 		{
 			CUEToolsUDC encoder = encodersBindingSource.Current as CUEToolsUDC;