diff --git a/src/Features/Core/Portable/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.StateManager.cs b/src/Features/Core/Portable/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.StateManager.cs
index 961ab055cee8b820535e6e361e23f32d63a7c9c7..643e80ff5918484af2e65fe17abe5bcb24574255 100644
--- a/src/Features/Core/Portable/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.StateManager.cs
+++ b/src/Features/Core/Portable/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.StateManager.cs
@@ -133,6 +133,12 @@ public ImmutableArray<StateSet> CreateBuildOnlyProjectStateSet(Project project)
 
                 // we always include compiler analyzer in build only state
                 var compilerAnalyzer = _analyzerManager.GetCompilerDiagnosticAnalyzer(project.Language);
+                if (compilerAnalyzer == null)
+                {
+                    // only way to get here is if MEF is corrupted.
+                    FailFast.OnFatalException(new Exception("How can this happen?"));
+                }
+
                 StateSet compilerStateSet;
                 if (hostStateSetMap.TryGetValue(compilerAnalyzer, out compilerStateSet))
                 {