diff --git a/Bullseye/Internal/TargetCollection.cs b/Bullseye/Internal/TargetCollection.cs
index 1ba0e7ba..7a47680e 100644
--- a/Bullseye/Internal/TargetCollection.cs
+++ b/Bullseye/Internal/TargetCollection.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
@@ -27,7 +28,7 @@ public async Task RunAsync(IEnumerable<string> names, bool skipDependencies, boo
 
             try
             {
-                var runningTargets = new Dictionary<string, Task>();
+                var runningTargets = new ConcurrentDictionary<string, Task>();
 
                 using (var sync = new SemaphoreSlim(1, 1))
                 {
@@ -54,7 +55,7 @@ public async Task RunAsync(IEnumerable<string> names, bool skipDependencies, boo
             await log.Succeeded(names).Tax();
         }
 
-        private async Task RunAsync(string name, IEnumerable<string> explicitTargets, bool skipDependencies, bool dryRun, bool parallel, Logger log, Func<Exception, bool> messageOnly, Dictionary<string, Task> runningTargets, SemaphoreSlim sync, Stack<string> dependencyStack)
+        private async Task RunAsync(string name, IEnumerable<string> explicitTargets, bool skipDependencies, bool dryRun, bool parallel, Logger log, Func<Exception, bool> messageOnly, ConcurrentDictionary<string, Task> runningTargets, SemaphoreSlim sync, Stack<string> dependencyStack)
         {
             dependencyStack.Push(name);
 
@@ -66,22 +67,7 @@ private async Task RunAsync(string name, IEnumerable<string> explicitTargets, bo
                     return;
                 }
 
-                bool gotValue;
-                Task runningTarget;
-
-                // cannot use WaitAsync() as it is not reentrant
-                sync.Wait();
-
-                try
-                {
-                    gotValue = runningTargets.TryGetValue(name, out runningTarget);
-                }
-                finally
-                {
-                    _ = sync.Release();
-                }
-
-                if (gotValue)
+                if (runningTargets.TryGetValue(name, out var runningTarget))
                 {
                     await log.Verbose(dependencyStack, "Awaiting...").Tax();
                     await runningTarget.Tax();
@@ -117,7 +103,7 @@ private async Task RunAsync(string name, IEnumerable<string> explicitTargets, bo
                         if (!runningTargets.TryGetValue(name, out runningTarget))
                         {
                             runningTarget = target.RunAsync(dryRun, parallel, log, messageOnly);
-                            runningTargets.Add(name, runningTarget);
+                            _ = runningTargets.TryAdd(name, runningTarget);
                         }
                     }
                     finally
diff --git a/BullseyeSmokeTester/Program.cs b/BullseyeSmokeTester/Program.cs
index e39638ce..4eb3747e 100644
--- a/BullseyeSmokeTester/Program.cs
+++ b/BullseyeSmokeTester/Program.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
 using System.Threading.Tasks;
@@ -101,8 +102,24 @@
 targets.Add("def", DependsOn("abc"), () => Console.Out.WriteLine("def"));
 targets.Add("default", DependsOn("def"));
 
+var largeGraph = new Targets();
+var largeGraphTargetNames = new List<string>();
+
+foreach (var name in Enumerable.Range(1, 30).Select(i => i.ToString(CultureInfo.InvariantCulture)))
+{
+    largeGraph.Add(name, largeGraphTargetNames.TakeLast(2), () => { });
+    largeGraphTargetNames.Add(name);
+}
+
+largeGraph.Add("large-graph", DependsOn(largeGraphTargetNames.Last()));
+
 var (options, targetNames) = Options.Parse(args);
 
+if (targetNames.Contains("large-graph"))
+{
+    await largeGraph.RunAndExitAsync(targetNames, options);
+}
+
 if (!options.ShowHelp)
 {
     await targets.RunWithoutExitingAsync(targetNames, options);
diff --git a/build.cmd b/build.cmd
index e4713350..09120d14 100644
--- a/build.cmd
+++ b/build.cmd
@@ -23,6 +23,8 @@ dotnet run -c Release --no-build -p BullseyeSmokeTester -- --verbose || goto :er
 dotnet run -c Release --no-build -p BullseyeSmokeTester -- -h --verbose || goto :error
 dotnet run -c Release --no-build -p BullseyeSmokeTester -- -h --verbose --no-color || goto :error
 
+dotnet run -c Release --no-build -p BullseyeSmokeTester -- large-graph --verbose --parallel || goto :error
+
 dotnet run -c Release --no-build -p BullseyeSmokeTester.DragonFruit  -- --help || goto :error
 dotnet run -c Release --no-build -p BullseyeSmokeTester.DragonFruit  -- --foo bar --verbose --targets build || goto :error
 
diff --git a/build.sh b/build.sh
index f0335c1f..cdfc0d9e 100755
--- a/build.sh
+++ b/build.sh
@@ -25,6 +25,8 @@ dotnet run -c Release --no-build -p BullseyeSmokeTester -- --verbose
 dotnet run -c Release --no-build -p BullseyeSmokeTester -- -h --verbose
 dotnet run -c Release --no-build -p BullseyeSmokeTester -- -h --verbose --no-color
 
+dotnet run -c Release --no-build -p BullseyeSmokeTester -- large-graph --verbose --parallel
+
 dotnet run -c Release --no-build -p BullseyeSmokeTester.DragonFruit  -- --help
 dotnet run -c Release --no-build -p BullseyeSmokeTester.DragonFruit  -- --foo bar --verbose --targets build