diff --git a/base/uk.ac.stfc.isis.ibex.configserver/src/uk/ac/stfc/isis/ibex/configserver/configuration/Macro.java b/base/uk.ac.stfc.isis.ibex.configserver/src/uk/ac/stfc/isis/ibex/configserver/configuration/Macro.java
index f23f15cd5e..9a6a734b23 100644
--- a/base/uk.ac.stfc.isis.ibex.configserver/src/uk/ac/stfc/isis/ibex/configserver/configuration/Macro.java
+++ b/base/uk.ac.stfc.isis.ibex.configserver/src/uk/ac/stfc/isis/ibex/configserver/configuration/Macro.java
@@ -37,7 +37,7 @@ public class Macro extends ModelObject {
 	 * The currently set value of the macro. If this is null the default is used.
 	 * Ideally an Optional should be here but GSON doesn't understand optionals :(
 	 */
-	private String value;
+	private String value = "";
 	/**
 	 * The description of the macro.
 	 */
diff --git a/base/uk.ac.stfc.isis.ibex.ui.configserver.tests/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/tests/MacroViewModelTest.java b/base/uk.ac.stfc.isis.ibex.ui.configserver.tests/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/tests/MacroViewModelTest.java
index 48932a8c4d..0c5825ceeb 100644
--- a/base/uk.ac.stfc.isis.ibex.ui.configserver.tests/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/tests/MacroViewModelTest.java
+++ b/base/uk.ac.stfc.isis.ibex.ui.configserver.tests/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/tests/MacroViewModelTest.java
@@ -101,7 +101,7 @@ public void test_GIVEN_macro_with_value_of_empty_string_WHEN_view_model_created_
     
     @Test
     public void test_GIVEN_macro_with_value_WHEN_view_model_created_THEN_use_default_is_false() {
-    	Macro m = new Macro("name", "A_VALUE", "description", "pattern", null, HasDefault.YES, true);
+    	Macro m = new Macro("name", "A_VALUE", "description", "pattern", null, HasDefault.YES, false);
         MacroViewModel macroViewModel = new MacroViewModel(m);
         
         boolean useDefault = macroViewModel.getUseDefault();
@@ -112,7 +112,7 @@ public void test_GIVEN_macro_with_value_WHEN_view_model_created_THEN_use_default
     @Test
     public void test_GIVEN_macro_with_value_WHEN_view_model_created_THEN_display_value_is_value() {
     	String expectedMacroValue = "A_VALUE";
-    	Macro m = new Macro("name", expectedMacroValue, "description", "pattern", null, HasDefault.YES, true);
+    	Macro m = new Macro("name", expectedMacroValue, "description", "pattern", null, HasDefault.YES, false);
         MacroViewModel macroViewModel = new MacroViewModel(m);
         
         String macroValue = macroViewModel.getDisplayValue();
@@ -146,7 +146,7 @@ public void test_GIVEN_macro_with_value_of_null_WHEN_use_default_set_false_THEN_
     	Macro m = new Macro("name", null, "description", "pattern", null, HasDefault.YES, true);
         MacroViewModel macroViewModel = new MacroViewModel(m);
         
-        macroViewModel.setUseDefault(false);
+        macroViewModel.setUseDefault(true);
         
         assertEquals("", m.getValue());
     }
diff --git a/base/uk.ac.stfc.isis.ibex.ui.configserver/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/MacroPanel.java b/base/uk.ac.stfc.isis.ibex.ui.configserver/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/MacroPanel.java
index e7126d2094..2b43bf2bfc 100644
--- a/base/uk.ac.stfc.isis.ibex.ui.configserver/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/MacroPanel.java
+++ b/base/uk.ac.stfc.isis.ibex.ui.configserver/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/MacroPanel.java
@@ -140,6 +140,7 @@ private Collection<Macro> makeDisplayMacroList(Collection<Macro> setMacros, Coll
 			displayMacros.add(displayMacro);
 			
 			displayMacro.addPropertyChangeListener("value", addSetMacroListener(displayMacro, setMacros));
+			displayMacro.addPropertyChangeListener("useDefault", onUseDefaultChangeListener(displayMacro, setMacros));
 		}
 		
 		return displayMacros;
@@ -164,4 +165,29 @@ public void propertyChange(PropertyChangeEvent newValue) {
 			}
 		};
 	}
-}
\ No newline at end of file
+
+	// If the Use Default flag is set or reset add or remove the selected macro from the set of existing Macros.
+	private PropertyChangeListener onUseDefaultChangeListener(final Macro displayMacro,
+			final Collection<Macro> setMacros) {
+		return new PropertyChangeListener() {
+			@Override
+			public void propertyChange(PropertyChangeEvent newValue) {
+				boolean useDefault = displayMacro.getUseDefault();
+				if (useDefault) {
+					setMacros.removeIf(m -> m.getName().equals(displayMacro.getName()));
+					return;
+				}
+
+				String macroValue = displayMacro.getValue() != null ? displayMacro.getValue() : "";
+				Optional<Macro> existingMacro = setMacros.stream()
+						.filter(m -> m.getName().equals(displayMacro.getName())).findFirst();
+				if (existingMacro.isPresent()) {
+					existingMacro.get().setValue(macroValue);
+					existingMacro.get().setUseDefault(false);
+				} else {
+					setMacros.add(new Macro(displayMacro));
+				}
+			}
+		};
+	}
+}
diff --git a/base/uk.ac.stfc.isis.ibex.ui.configserver/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/MacroViewModel.java b/base/uk.ac.stfc.isis.ibex.ui.configserver/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/MacroViewModel.java
index 4aa685001b..68b3a97eca 100644
--- a/base/uk.ac.stfc.isis.ibex.ui.configserver/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/MacroViewModel.java
+++ b/base/uk.ac.stfc.isis.ibex.ui.configserver/src/uk/ac/stfc/isis/ibex/ui/configserver/editing/macros/MacroViewModel.java
@@ -19,7 +19,7 @@ public class MacroViewModel extends ModelObject {
 	public MacroViewModel(Macro macro) {
 		this.macro = macro;
 		macro.addPropertyChangeListener("value", passThrough());
-		setUseDefault((macro.getValue() == null) || (macro.getValue().equals("")));
+		macro.addPropertyChangeListener("useDefault", passThrough());
 	}
 
 	/**
@@ -100,7 +100,7 @@ public String getDisplayDefault() {
 	 */
 	public String getDisplayValue() {
 		String macroDisplayVal = "(default)";
-		if (macro.getValue() != "") {
+		if (!macro.getUseDefault()) {
 			macroDisplayVal = macro.getValue();
 		}
 		return macroDisplayVal;