diff --git a/extensions/s3/src/main/java/io/deephaven/extensions/s3/S3ChannelContext.java b/extensions/s3/src/main/java/io/deephaven/extensions/s3/S3ChannelContext.java
index 78420954697..15bbed956c9 100644
--- a/extensions/s3/src/main/java/io/deephaven/extensions/s3/S3ChannelContext.java
+++ b/extensions/s3/src/main/java/io/deephaven/extensions/s3/S3ChannelContext.java
@@ -32,6 +32,7 @@ final class S3ChannelContext extends BaseSeekableChannelContext implements Seeka
     static final long UNINITIALIZED_SIZE = -1;
     private static final long UNINITIALIZED_NUM_FRAGMENTS = -1;
 
+    final S3SeekableChannelProvider provider;
     final S3AsyncClient client;
     final S3Instructions instructions;
 
@@ -63,8 +64,12 @@ final class S3ChannelContext extends BaseSeekableChannelContext implements Seeka
      */
     private long numFragments;
 
-    S3ChannelContext(@NotNull final S3AsyncClient client, @NotNull final S3Instructions instructions,
+    S3ChannelContext(
+            @NotNull final S3SeekableChannelProvider provider,
+            @NotNull final S3AsyncClient client,
+            @NotNull final S3Instructions instructions,
             @NotNull final S3RequestCache sharedCache) {
+        this.provider = Objects.requireNonNull(provider);
         this.client = Objects.requireNonNull(client);
         this.instructions = Objects.requireNonNull(instructions);
         this.localCache = new S3Request.AcquiredRequest[instructions.maxCacheSize()];
@@ -88,7 +93,7 @@ void setURI(@NotNull final S3Uri uri) {
         this.uri = uri;
     }
 
-    void verifyOrSetSize(long size) {
+    void verifyOrSetSize(final long size) {
         if (this.size == UNINITIALIZED_SIZE) {
             setSize(size);
         } else if (this.size != size) {
@@ -255,10 +260,12 @@ private void ensureSize() throws IOException {
         } catch (final InterruptedException | ExecutionException | TimeoutException | CancellationException e) {
             throw handleS3Exception(e, String.format("fetching HEAD for file %s, %s", uri, ctxStr()), instructions);
         }
-        setSize(headObjectResponse.contentLength());
+        final long fileSize = headObjectResponse.contentLength();
+        setSize(fileSize);
+        provider.updateFileSizeCache(uri.uri(), fileSize);
     }
 
-    private void setSize(long size) {
+    private void setSize(final long size) {
         this.size = size;
         // ceil(size / fragmentSize)
         this.numFragments = (size + instructions.fragmentSize() - 1) / instructions.fragmentSize();
diff --git a/extensions/s3/src/main/java/io/deephaven/extensions/s3/S3SeekableChannelProvider.java b/extensions/s3/src/main/java/io/deephaven/extensions/s3/S3SeekableChannelProvider.java
index 1b52ca3ac54..b87401e42bb 100644
--- a/extensions/s3/src/main/java/io/deephaven/extensions/s3/S3SeekableChannelProvider.java
+++ b/extensions/s3/src/main/java/io/deephaven/extensions/s3/S3SeekableChannelProvider.java
@@ -96,12 +96,12 @@ public InputStream getInputStream(final SeekableByteChannel channel) {
 
     @Override
     public SeekableChannelContext makeContext() {
-        return new S3ChannelContext(s3AsyncClient, s3Instructions, sharedCache);
+        return new S3ChannelContext(this, s3AsyncClient, s3Instructions, sharedCache);
     }
 
     @Override
     public SeekableChannelContext makeSingleUseContext() {
-        return new S3ChannelContext(s3AsyncClient, s3Instructions.singleUse(), sharedCache);
+        return new S3ChannelContext(this, s3AsyncClient, s3Instructions.singleUse(), sharedCache);
     }
 
     @Override
@@ -208,7 +208,7 @@ private void fetchNextBatch() throws IOException {
                                         + s3Object.key() + " and bucket " + bucketName + " inside directory "
                                         + directory, e);
                             }
-                            updateFileSizeCache(getFileSizeCache(), uri, s3Object.size());
+                            updateFileSizeCache(uri, s3Object.size());
                             return uri;
                         }).iterator();
                 // The following token is null when the last batch is fetched.
@@ -235,12 +235,10 @@ private Map<URI, FileSizeInfo> getFileSizeCache() {
     }
 
     /**
-     * Update the given file size cache with the given URI and size.
+     * Cache the file size for the given URI.
      */
-    private static void updateFileSizeCache(
-            @NotNull final Map<URI, FileSizeInfo> fileSizeCache,
-            @NotNull final URI uri,
-            final long size) {
+    void updateFileSizeCache(@NotNull final URI uri, final long size) {
+        final Map<URI, FileSizeInfo> fileSizeCache = getFileSizeCache();
         fileSizeCache.compute(uri, (key, existingInfo) -> {
             if (existingInfo == null) {
                 return new FileSizeInfo(uri, size);