diff --git a/docs/Makefile b/docs/Makefile
index 0352c612..4c1d2b26 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -17,6 +17,7 @@ MANUAL_PAGES := 			\
 PRUNE_SIMULATOR_FILES := 					\
 	prune-simulator/index.html				\
 	prune-simulator/documentation.html			\
+	prune-simulator/clear-trigger.png			\
 	prune-simulator/prune-simulator.js
 
 # Sphinx documentation setup
diff --git a/docs/prune-simulator/clear-trigger.png b/docs/prune-simulator/clear-trigger.png
new file mode 100644
index 00000000..cc374cf2
Binary files /dev/null and b/docs/prune-simulator/clear-trigger.png differ
diff --git a/docs/prune-simulator/index.html b/docs/prune-simulator/index.html
index 641ef435..861d560b 100644
--- a/docs/prune-simulator/index.html
+++ b/docs/prune-simulator/index.html
@@ -33,6 +33,9 @@
         .first-of-month {
             border-right: dashed black 4px;
         }
+        .clear-trigger {
+            background-image: url(./clear-trigger.png);
+        }
     </style>
 
     <script type="text/javascript" src="extjs/ext-all.js"></script>
diff --git a/docs/prune-simulator/prune-simulator.js b/docs/prune-simulator/prune-simulator.js
index 48c0a968..5533c2d6 100644
--- a/docs/prune-simulator/prune-simulator.js
+++ b/docs/prune-simulator/prune-simulator.js
@@ -265,6 +265,34 @@ Ext.onReady(function() {
 	},
     });
 
+    Ext.define('PBS.PruneSimulatorKeepInput', {
+	extend: 'Ext.form.field.Number',
+	alias: 'widget.prunesimulatorKeepInput',
+
+	allowBlank: true,
+	fieldGroup: 'keep',
+	minValue: 1,
+
+	listeners: {
+	    afterrender: function(field) {
+		this.triggers.clear.setVisible(field.value !== null);
+	    },
+	    change: function(field, newValue, oldValue) {
+		this.triggers.clear.setVisible(newValue !== null);
+	    },
+	},
+	triggers: {
+	    clear: {
+		cls: 'clear-trigger',
+		weight: -1,
+		handler: function() {
+		    this.triggers.clear.setVisible(false);
+		    this.setValue(null);
+		},
+	    },
+	},
+    });
+
     Ext.define('PBS.PruneSimulatorPanel', {
 	extend: 'Ext.panel.Panel',
 	alias: 'widget.prunesimulatorPanel',
@@ -560,58 +588,37 @@ Ext.onReady(function() {
 
 	keepItems: [
 	    {
-		xtype: 'numberfield',
+		xtype: 'prunesimulatorKeepInput',
 		name: 'keep-last',
-		allowBlank: true,
 		fieldLabel: 'keep-last',
-		minValue: 0,
 		value: 4,
-		fieldGroup: 'keep',
 	    },
 	    {
-		xtype: 'numberfield',
+		xtype: 'prunesimulatorKeepInput',
 		name: 'keep-hourly',
-		allowBlank: true,
 		fieldLabel: 'keep-hourly',
-		minValue: 0,
-		value: 0,
-		fieldGroup: 'keep',
 	    },
 	    {
-		xtype: 'numberfield',
+		xtype: 'prunesimulatorKeepInput',
 		name: 'keep-daily',
-		allowBlank: true,
 		fieldLabel: 'keep-daily',
-		minValue: 0,
 		value: 5,
-		fieldGroup: 'keep',
 	    },
 	    {
-		xtype: 'numberfield',
+		xtype: 'prunesimulatorKeepInput',
 		name: 'keep-weekly',
-		allowBlank: true,
 		fieldLabel: 'keep-weekly',
-		minValue: 0,
 		value: 2,
-		fieldGroup: 'keep',
 	    },
 	    {
-		xtype: 'numberfield',
+		xtype: 'prunesimulatorKeepInput',
 		name: 'keep-monthly',
-		allowBlank: true,
 		fieldLabel: 'keep-monthly',
-		minValue: 0,
-		value: 0,
-		fieldGroup: 'keep',
 	    },
 	    {
-		xtype: 'numberfield',
+		xtype: 'prunesimulatorKeepInput',
 		name: 'keep-yearly',
-		allowBlank: true,
 		fieldLabel: 'keep-yearly',
-		minValue: 0,
-		value: 0,
-		fieldGroup: 'keep',
 	    },
 	],