diff --git a/Indicators/McClellanOscillator.cs b/Indicators/McClellanOscillator.cs
index 51b139b99f81..bc3fe4814929 100644
--- a/Indicators/McClellanOscillator.cs
+++ b/Indicators/McClellanOscillator.cs
@@ -50,7 +50,9 @@ public class McClellanOscillator : TradeBarIndicator, IIndicatorWarmUpPeriodProv
         /// <summary>
         /// Required period, in data points, for the indicator to be ready and fully initialized.
         /// </summary>
-        public int WarmUpPeriod => EMASlow.WarmUpPeriod + ADDifference.WarmUpPeriod;
+        /// <remarks>The two periods share a bar: EMASlow is fed by ADDifference and only
+        /// once it is ready, so ADDifference's last warm-up bar is EMASlow's first input.</remarks>
+        public int WarmUpPeriod => EMASlow.WarmUpPeriod + ADDifference.WarmUpPeriod - 1;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="McClellanOscillator"/> class
diff --git a/Tests/Indicators/McClellanOscillatorTests.cs b/Tests/Indicators/McClellanOscillatorTests.cs
index 90d7811a3f62..de26030b37b9 100644
--- a/Tests/Indicators/McClellanOscillatorTests.cs
+++ b/Tests/Indicators/McClellanOscillatorTests.cs
@@ -58,11 +58,12 @@ public override void WarmsUpProperly()
                 indicator.Update(new TradeBar() { Symbol = Symbols.AAPL, Close = i, Volume = 1, Time = reference.AddMinutes(i) });
                 indicator.Update(new TradeBar() { Symbol = Symbols.MSFT, Close = i, Volume = 1, Time = reference.AddMinutes(i) });
                 indicator.Update(new TradeBar() { Symbol = Symbols.GOOG, Close = i, Volume = 1, Time = reference.AddMinutes(i) });
+
+                Assert.AreEqual(i == indicator.WarmUpPeriod, indicator.IsReady);
             }
 
             Assert.AreEqual(0m, indicator.Current.Value);
             Assert.AreEqual(indicator.WarmUpPeriod * 3, indicator.Samples);
-            Assert.IsTrue(indicator.IsReady);
         }
 
         [Test]
diff --git a/Tests/Indicators/McClellanSummationIndexTests.cs b/Tests/Indicators/McClellanSummationIndexTests.cs
index 919babcdd987..95848d36f100 100644
--- a/Tests/Indicators/McClellanSummationIndexTests.cs
+++ b/Tests/Indicators/McClellanSummationIndexTests.cs
@@ -57,11 +57,12 @@ public override void WarmsUpProperly()
                 indicator.Update(new TradeBar() { Symbol = Symbols.AAPL, Close = i, Volume = 1, Time = reference.AddMinutes(i) });
                 indicator.Update(new TradeBar() { Symbol = Symbols.MSFT, Close = i, Volume = 1, Time = reference.AddMinutes(i) });
                 indicator.Update(new TradeBar() { Symbol = Symbols.GOOG, Close = i, Volume = 1, Time = reference.AddMinutes(i) });
+
+                Assert.AreEqual(i == indicator.WarmUpPeriod, indicator.IsReady);
             }
 
             Assert.AreEqual(60m, indicator.Current.Value);
             Assert.AreEqual(indicator.WarmUpPeriod * 3, indicator.Samples);
-            Assert.IsTrue(indicator.IsReady);
         }
 
         [Test]