diff --git a/app/databrowser/src/main/java/org/csstudio/trends/databrowser3/model/FormulaItem.java b/app/databrowser/src/main/java/org/csstudio/trends/databrowser3/model/FormulaItem.java
index fdc3404ed5..2ee6b747e8 100644
--- a/app/databrowser/src/main/java/org/csstudio/trends/databrowser3/model/FormulaItem.java
+++ b/app/databrowser/src/main/java/org/csstudio/trends/databrowser3/model/FormulaItem.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2010-2019 Oak Ridge National Laboratory.
+ * Copyright (c) 2010-2022 Oak Ridge National Laboratory.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -75,7 +75,7 @@ public class FormulaItem extends ModelItem
     /** Samples of the formula, computed from inputs.
      *  Access must lock samples
      */
-    private final PlotSampleArray samples = new PlotSampleArray();
+    private final FormulaSamples samples = new FormulaSamples();
 
     /** Initialize formula
      *  @param name Name of the Formula item
@@ -285,6 +285,7 @@ else if (org.phoebus.core.vtypes.VTypeHelper.getTimestamp(values[i]).compareTo(t
         {
             logger.log(Level.WARNING, "Error computing " + this, ex);
         }
+
         // Update PlotSamples
         samples.set(result);
     }
diff --git a/app/databrowser/src/main/java/org/csstudio/trends/databrowser3/model/FormulaSamples.java b/app/databrowser/src/main/java/org/csstudio/trends/databrowser3/model/FormulaSamples.java
new file mode 100644
index 0000000000..48a310e2a4
--- /dev/null
+++ b/app/databrowser/src/main/java/org/csstudio/trends/databrowser3/model/FormulaSamples.java
@@ -0,0 +1,55 @@
+/*******************************************************************************
+ * Copyright (c) 2022 Oak Ridge National Laboratory.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ ******************************************************************************/
+package org.csstudio.trends.databrowser3.model;
+
+import java.time.Instant;
+
+import org.epics.vtype.AlarmSeverity;
+import org.phoebus.archive.vtype.VTypeHelper;
+
+/** Samples of a {@link FormulaItem}.
+
+ *  <p>If the last sample is valid, it's
+ *  extended to 'now' assuming no new data means
+ *  that the last value is still valid.
+ *
+ *  @author Kay Kasemir
+ */
+public class FormulaSamples extends PlotSampleArray
+{
+    /** @return Sample count, includes the last sample extended to 'now' */
+    @Override
+    public int size()
+    {
+        final int raw = super.size();
+        if (raw <= 0)
+            return raw;
+        final PlotSample last = get(raw-1);
+        if (org.phoebus.core.vtypes.VTypeHelper.getSeverity(last.getVType()) == AlarmSeverity.UNDEFINED)
+            return raw;
+        // Last sample is valid, so it should still apply 'now'
+        return raw+1;
+    }
+
+    /** @param index 0... size()-1
+     *  @return Sample from historic or live sample subsection
+     */
+    @Override
+    public PlotSample get(final int index)
+    {
+        final int raw_count = super.size();
+        if (index < raw_count)
+            return super.get(index);
+        // Last sample is valid, so it should still apply 'now'
+        final PlotSample sample = super.get(raw_count-1);
+        if (Instant.now().compareTo(sample.getPosition()) < 0)
+            return sample;
+        else
+            return new PlotSample(sample.getSource(), VTypeHelper.transformTimestampToNow(sample.getVType()));
+    }
+}
diff --git a/core/pv/src/test/java/org/phoebus/pv/FormulaTest.java b/core/pv/src/test/java/org/phoebus/pv/FormulaTest.java
index 9e8ed5334d..493f9c50fb 100644
--- a/core/pv/src/test/java/org/phoebus/pv/FormulaTest.java
+++ b/core/pv/src/test/java/org/phoebus/pv/FormulaTest.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2020-2021 Oak Ridge National Laboratory.
+ * Copyright (c) 2020-2022 Oak Ridge National Laboratory.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -223,4 +223,44 @@ public void raceDemo() throws Exception
         // With plain but real PV, often get the initial value right away.
         assertEquals(2, updates.get());
     }
+
+    @Test
+    public void testUpdatingVsConstant() throws Exception
+    {
+        // Formula with input that changes
+        {
+            final PV pv = PVPool.getPV("=`sim://sine`");
+            final CountDownLatch updates = new CountDownLatch(1);
+            final Disposable sub = pv.onValueEvent().subscribe(value ->
+            {
+                System.out.println(pv.getName() + " = " + value);
+                if (! PV.isDisconnected(value))
+                    updates.countDown();
+            });
+
+            final boolean got_value = updates.await(5, TimeUnit.SECONDS);
+            sub.dispose();
+            PVPool.releasePV(pv);
+
+            assertTrue(got_value);
+        }
+
+        // Try again with local PV that does not change
+        {
+            final PV pv = PVPool.getPV("=`loc://constant(42)`");
+            final CountDownLatch updates = new CountDownLatch(1);
+            final Disposable sub = pv.onValueEvent().subscribe(value ->
+            {
+                System.out.println(pv.getName() + " = " + value);
+                if (! PV.isDisconnected(value))
+                    updates.countDown();
+            });
+
+            final boolean got_value = updates.await(5, TimeUnit.SECONDS);
+            sub.dispose();
+            PVPool.releasePV(pv);
+
+            assertTrue(got_value);
+        }
+    }
 }