diff --git a/src/Sarif/EnumeratedArtifact.cs b/src/Sarif/EnumeratedArtifact.cs
index 0a6311ada..b3004d191 100644
--- a/src/Sarif/EnumeratedArtifact.cs
+++ b/src/Sarif/EnumeratedArtifact.cs
@@ -19,7 +19,6 @@ public EnumeratedArtifact(IFileSystem fileSystem)
         internal byte[] bytes;
         internal string contents;
 
-        private bool? isBinary;
         private Encoding encoding;
 
         public Uri Uri { get; set; }
@@ -28,22 +27,11 @@ public bool IsBinary
         {
             get
             {
-                return this.isBinary ?? IsArtifactBinary();
+                GetArtifactData();
+                return this.contents == null;
             }
         }
 
-        internal bool IsArtifactBinary()
-        {
-            if (isBinary.HasValue)
-            {
-                return isBinary.Value;
-            }
-
-            GetArtifactData();
-            this.isBinary = this.contents == null;
-            return this.isBinary.Value;
-        }
-
         public Stream Stream { get; set; }
 
         public Encoding Encoding
@@ -151,7 +139,7 @@ private void RetrieveDataFromSeekableStream()
             // Reset to beginning of stream in case caller neglected to do so.
             this.Stream.Seek(0, SeekOrigin.Begin);
 
-            byte[] header = new byte[4096];
+            byte[] header = new byte[1024];
             int length = this.Stream.Read(header, 0, header.Length);
             isText = FileEncoding.CheckForTextualData(header, 0, length, out this.encoding);
 
diff --git a/src/Sarif/MultithreadedZipArchiveArtifactProvider.cs b/src/Sarif/MultithreadedZipArchiveArtifactProvider.cs
index 42115849f..4fcb8d6d7 100644
--- a/src/Sarif/MultithreadedZipArchiveArtifactProvider.cs
+++ b/src/Sarif/MultithreadedZipArchiveArtifactProvider.cs
@@ -12,8 +12,8 @@ public class MultithreadedZipArchiveArtifactProvider : ArtifactProvider
         private readonly ZipArchive zipArchive;
         private ISet<string> binaryExtensions;
 
-        public ISet<string> BinaryExtensions 
-        { 
+        public ISet<string> BinaryExtensions
+        {
             get
             {
                 this.binaryExtensions ??= CreateDefaultBinaryExtensionsSet();
diff --git a/src/Test.UnitTests.Sarif/EnumeratedArtifactTests.cs b/src/Test.UnitTests.Sarif/EnumeratedArtifactTests.cs
index d731cf49d..b2bbf3585 100644
--- a/src/Test.UnitTests.Sarif/EnumeratedArtifactTests.cs
+++ b/src/Test.UnitTests.Sarif/EnumeratedArtifactTests.cs
@@ -221,6 +221,7 @@ private void ValidateBinaryArtifact(EnumeratedArtifact artifact, int sizeInBytes
             artifact.Bytes.Should().NotBeNull();
             artifact.Bytes.Length.Should().Be(sizeInBytes);
             artifact.SizeInBytes.Should().Be(sizeInBytes);
+            artifact.IsBinary.Should().BeTrue();
 
             artifact.Contents.Should().BeNull();
         }
@@ -230,6 +231,7 @@ private void ValidateTextArtifact(EnumeratedArtifact artifact, int sizeInBytes)
             artifact.Contents.Should().NotBeNull();
             artifact.Contents.Length.Should().Be(sizeInBytes);
             artifact.SizeInBytes.Should().Be(sizeInBytes);
+            artifact.IsBinary.Should().BeFalse();
 
             artifact.Bytes.Should().BeNull();
         }