diff --git a/lib/std/Io/File/Reader.zig b/lib/std/Io/File/Reader.zig
index ca442bf54a1d0653e20e7afff3a682880eae90a5..35cf676f4ae97dfa1391b9d90649348665500f73 100644
--- a/lib/std/Io/File/Reader.zig
+++ b/lib/std/Io/File/Reader.zig
@@ -154,7 +154,6 @@ pub fn seekBy(r: *Reader, offset: i64) SeekError!void {
                     return err;
                 };
             }
-            r.interface.tossBuffered();
         },
         .failure => return r.seek_err.?,
     }
diff --git a/lib/std/fs/test.zig b/lib/std/fs/test.zig
index 981bc75d442a3688f43224d4dfe278c03ea3f5a8..9104a229b85c0839324deb34e536282e34a7baf9 100644
--- a/lib/std/fs/test.zig
+++ b/lib/std/fs/test.zig
@@ -2409,13 +2409,19 @@ test "seekBy" {
     try tmp_dir.dir.writeFile(io, .{ .sub_path = "blah.txt", .data = "let's test seekBy" });
     const f = try tmp_dir.dir.openFile(io, "blah.txt", .{ .mode = .read_only });
     defer f.close(io);
-    var reader = f.readerStreaming(io, &.{});
+    var buf: [10]u8 = undefined;
+    var reader = f.readerStreaming(io, &buf);
+    // Seek without any buffered data
+    try reader.seekBy(2);
+
+    // Seek when the buffered data is sufficient to satisfy the seek amount
+    try reader.interface.fill(2);
     try reader.seekBy(2);
 
     var buffer: [20]u8 = undefined;
     const n = try reader.interface.readSliceShort(&buffer);
-    try expectEqual(15, n);
-    try expectEqualStrings("t's test seekBy", buffer[0..15]);
+    try expectEqual(13, n);
+    try expectEqualStrings("s test seekBy", buffer[0..n]);
 }
 
 test "seekTo flushes buffered data" {