diff --git a/core/iwasm/libraries/lib-wasi-threads/tid_allocator.c b/core/iwasm/libraries/lib-wasi-threads/tid_allocator.c
index dc2d4f1bca..d7f6c74548 100644
--- a/core/iwasm/libraries/lib-wasi-threads/tid_allocator.c
+++ b/core/iwasm/libraries/lib-wasi-threads/tid_allocator.c
@@ -8,7 +8,10 @@
 #include "bh_log.h"
 
 bh_static_assert(TID_MIN <= TID_MAX);
+/* Some platforms, like Zephyr, have already defined MIN at this point */
+#ifndef MIN
 #define MIN(a, b) (((a) < (b)) ? (a) : (b))
+#endif
 
 bool
 tid_allocator_init(TidAllocator *tid_allocator)
diff --git a/core/shared/platform/zephyr/zephyr_file.c b/core/shared/platform/zephyr/zephyr_file.c
index f585002e07..54b357e318 100644
--- a/core/shared/platform/zephyr/zephyr_file.c
+++ b/core/shared/platform/zephyr/zephyr_file.c
@@ -594,8 +594,9 @@ os_preadv(os_file_handle handle, const struct __wasi_iovec_t *iov, int iovcnt,
 
         total_read += bytes_read;
 
-        // If we read less than we asked for, stop reading
-        if (bytes_read < iov[i].buf_len) {
+        /*  If we read less than we asked for, stop reading
+            bytes_read being a non-negative value was already checked */
+        if ((size_t)bytes_read < iov[i].buf_len) {
             break;
         }
     }
@@ -630,8 +631,9 @@ os_pwritev(os_file_handle handle, const struct __wasi_ciovec_t *iov, int iovcnt,
 
         total_written += bytes_written;
 
-        // If we wrote less than we asked for, stop writing
-        if (bytes_written < iov[i].buf_len) {
+        /*  If we wrote less than we asked for, stop writing
+            bytes_read being a non-negative value was already checked */
+        if ((size_t)bytes_written < iov[i].buf_len) {
             break;
         }
     }
@@ -660,8 +662,9 @@ os_readv(os_file_handle handle, const struct __wasi_iovec_t *iov, int iovcnt,
 
         total_read += bytes_read;
 
-        // If we read less than we asked for, stop reading
-        if (bytes_read < iov[i].buf_len) {
+        /*  If we read less than we asked for, stop reading
+            bytes_read being a non-negative value was already checked */
+        if ((size_t)bytes_read < iov[i].buf_len) {
             break;
         }
     }
@@ -705,8 +708,9 @@ os_writev(os_file_handle handle, const struct __wasi_ciovec_t *iov, int iovcnt,
 
         total_written += bytes_written;
 
-        // If we wrote less than we asked for, stop writing
-        if (bytes_written < iov[i].buf_len) {
+        /*  If we wrote less than we asked for, stop writing
+            bytes_read being a non-negative value was already checked */
+        if ((size_t)bytes_written < iov[i].buf_len) {
             break;
         }
     }