diff --git a/src/Sarif/EnumeratedArtifact.cs b/src/Sarif/EnumeratedArtifact.cs
index b3004d191..4a8419520 100644
--- a/src/Sarif/EnumeratedArtifact.cs
+++ b/src/Sarif/EnumeratedArtifact.cs
@@ -93,7 +93,7 @@ public byte[] Bytes
                 }
 
                 // This is our client-side, disk-based file retrieval case.
-                Stream = FileSystem.FileOpenRead(Uri.LocalPath);
+                this.Stream = FileSystem.FileOpenRead(Uri.LocalPath);
             }
 
             if (Stream.CanSeek)
@@ -105,7 +105,7 @@ public byte[] Bytes
                 RetrieveDataFromNonSeekableStream();
             }
 
-            Stream = null;
+            this.Stream = null;
 
             return (this.contents, this.bytes);
         }
diff --git a/src/Sarif/ZipArchiveArtifact.cs b/src/Sarif/ZipArchiveArtifact.cs
index 081dee6d2..04f3c7a2f 100644
--- a/src/Sarif/ZipArchiveArtifact.cs
+++ b/src/Sarif/ZipArchiveArtifact.cs
@@ -21,8 +21,9 @@ public class ZipArchiveArtifact : IEnumeratedArtifact
 
         public ZipArchiveArtifact(ZipArchive archive, ZipArchiveEntry entry, ISet<string> binaryExtensions)
         {
-            this.entry = entry;
-            this.archive = archive;
+            this.entry = entry ?? throw new ArgumentNullException(nameof(entry));
+            this.archive = archive ?? throw new ArgumentNullException(nameof(archive));
+
             this.binaryExtensions = binaryExtensions;
             this.uri = new Uri(entry.FullName, UriKind.RelativeOrAbsolute);
         }
@@ -35,9 +36,7 @@ public Stream Stream
             {
                 lock (this.archive)
                 {
-                    return entry != null
-                        ? entry.Open()
-                        : null;
+                    return entry.Open();
                 }
             }
             set => throw new NotImplementedException();