diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Attribute.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Attribute.cs
index 08e8f391a342..a70b84dde1df 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Attribute.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Attribute.cs
@@ -91,7 +91,7 @@ private void ExtractArguments(TextWriter trapFile)
                     // The current argument is not named
                     // so the previous ones were also not named
                     // so the child index matches the parameter index.
-                    isParamsParameter = Symbol?.AttributeConstructor?.Parameters[childIndex].IsParams == true;
+                    isParamsParameter = Symbol.AttributeConstructor?.Parameters[childIndex].IsParams == true;
                     argSyntax = ctorArguments[childIndex];
                 }
 
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/NonGeneratedSourceLocation.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/NonGeneratedSourceLocation.cs
index f479f607e9cb..e3e3c0c6ae4a 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp/Entities/NonGeneratedSourceLocation.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp/Entities/NonGeneratedSourceLocation.cs
@@ -22,7 +22,7 @@ public override void Populate(TextWriter trapFile)
                 Position.Span.Start.Line + 1, Position.Span.Start.Character + 1,
                 Position.Span.End.Line + 1, Position.Span.End.Character);
 
-            var mapped = Symbol!.GetMappedLineSpan();
+            var mapped = Symbol.GetMappedLineSpan();
             if (mapped.HasMappedPath && mapped.IsValid)
             {
                 var mappedLoc = Create(Context, Location.Create(mapped.Path, default, mapped.Span));
diff --git a/csharp/extractor/Semmle.Extraction/Entities/Base/CachedEntity`1.cs b/csharp/extractor/Semmle.Extraction/Entities/Base/CachedEntity`1.cs
index 4ef36362733c..82ded71a9cd5 100644
--- a/csharp/extractor/Semmle.Extraction/Entities/Base/CachedEntity`1.cs
+++ b/csharp/extractor/Semmle.Extraction/Entities/Base/CachedEntity`1.cs
@@ -1,3 +1,4 @@
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using Microsoft.CodeAnalysis;
 
@@ -30,6 +31,7 @@ protected CachedEntity(Context context) : base(context)
     /// <typeparam name="TSymbol">The type of the symbol.</typeparam>
     public abstract class CachedEntity<TSymbol> : CachedEntity where TSymbol : notnull
     {
+        [NotNull]
         public TSymbol Symbol { get; }
 
         protected CachedEntity(Context context, TSymbol symbol) : base(context)