diff --git a/setup.py b/setup.py
index c95222756..292f0f603 100644
--- a/setup.py
+++ b/setup.py
@@ -783,7 +783,9 @@ class pil_build_ext(build_ext):
             if _find_include_file(self, "jxl/encode.h") and _find_include_file(
                 self, "jxl/decode.h"
             ):
-                if _find_library_file(self, "jxl"):
+                if _find_library_file(self, "jxl") and _find_library_file(
+                    self, "jxl_threads"
+                ):
                     feature.set("jpegxl", "jxl")
 
         if feature.want("imagequant"):
@@ -1012,7 +1014,6 @@ class pil_build_ext(build_ext):
 
         jpegxl = feature.get("jpegxl")
         if isinstance(jpegxl, str):
-            # jxl and jxl_threads are required
             libs = [jpegxl, jpegxl + "_threads"]
             self._update_extension("PIL._jpegxl", libs)
         else:
diff --git a/src/_jpegxl.c b/src/_jpegxl.c
index b812061f6..3bb3d7f26 100644
--- a/src/_jpegxl.c
+++ b/src/_jpegxl.c
@@ -1,6 +1,5 @@
 #define PY_SSIZE_T_CLEAN
 #include <Python.h>
-#include <stdbool.h>
 #include "libImaging/Imaging.h"
 
 #include <jxl/codestream_header.h>
@@ -295,8 +294,8 @@ decoder_loop_skip_process:
             decp->status = JxlDecoderGetBoxType(decp->decoder, btype, JXL_TRUE);
             _JXL_CHECK("JxlDecoderGetBoxType");
 
-            bool is_box_exif = !memcmp(btype, "Exif", 4);
-            bool is_box_xmp = !memcmp(btype, "xml ", 4);
+            int is_box_exif = !memcmp(btype, "Exif", 4);
+            int is_box_xmp = !memcmp(btype, "xml ", 4);
             if (!is_box_exif && !is_box_xmp) {
                 // not exif/xmp box so continue
                 continue;
@@ -472,6 +471,7 @@ end:
         decp->status
     );
     PyErr_SetString(PyExc_OSError, err_msg);
+    return NULL;
 }
 
 PyObject *
@@ -562,7 +562,6 @@ setup_module(PyObject *m) {
         return -1;
     }
 
-    // TODO(oloke) ready object types?
     PyObject *d = PyModule_GetDict(m);
     PyObject *v = PyUnicode_FromString(JpegXlDecoderVersion_str());
     PyDict_SetItemString(d, "libjxl_version", v ? v : Py_None);