diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index 9000e9a442d877a89146283d635f0d6dc0cd8550..6361963ab4d898bcf84a08fed641c7390e476e4a 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -1717,6 +1717,7 @@ pub const Object = struct {
     }
 
     pub fn updateContainerType(o: *Object, pt: Zcu.PerThread, ty: InternPool.Index, success: bool) Allocator.Error!void {
+        _ = o.type_map.remove(ty);
         try o.type_pool.updateContainerType(pt, .{ .llvm = o }, ty, success);
         if (o.named_enum_map.get(ty)) |function_index| {
             try o.updateIsNamedEnumValueFunction(.fromInterned(ty), function_index);
diff --git a/test/incremental/increase_array_field_length b/test/incremental/increase_array_field_length
new file mode 100644
index 0000000000000000000000000000000000000000..714473dd8302d57b0b2644a90f73442d47e9db2d
--- /dev/null
+++ b/test/incremental/increase_array_field_length
@@ -0,0 +1,31 @@
+#update=initial version
+#file=main.zig
+const Big = struct { arr: [10]u8 };
+pub fn main(init: std.process.Init) !void {
+    var big: Big = undefined;
+    big = .{ .arr = @splat(123) };
+    var stdout_writer = std.Io.File.stdout().writerStreaming(init.io, &.{});
+    const index = big.arr.len - 1;
+    big.arr[index] = 234;
+    stdout_writer.interface.print("arr[{d}] = {d}\n", .{ index, big.arr[index] }) catch |err| switch (err) {
+        error.WriteFailed => return stdout_writer.err.?,
+    };
+}
+const std = @import("std");
+#expect_stdout="arr[9] = 234\n"
+
+#update=increase array length
+#file=main.zig
+const Big = struct { arr: [1000]u8 };
+pub fn main(init: std.process.Init) !void {
+    var big: Big = undefined;
+    big = .{ .arr = @splat(123) };
+    var stdout_writer = std.Io.File.stdout().writerStreaming(init.io, &.{});
+    const index = big.arr.len - 1;
+    big.arr[index] = 234;
+    stdout_writer.interface.print("arr[{d}] = {d}\n", .{ index, big.arr[index] }) catch |err| switch (err) {
+        error.WriteFailed => return stdout_writer.err.?,
+    };
+}
+const std = @import("std");
+#expect_stdout="arr[999] = 234\n"