diff --git a/shared-bindings/zlib/__init__.c b/shared-bindings/zlib/__init__.c
index d0fd803d3a..1b38d59ff4 100644
--- a/shared-bindings/zlib/__init__.c
+++ b/shared-bindings/zlib/__init__.c
@@ -71,12 +71,12 @@
 //|     ...
 //|
 STATIC mp_obj_t zlib_decompress(size_t n_args, const mp_obj_t *args) {
-    bool is_zlib = true;
-    if (n_args > 1 && MP_OBJ_SMALL_INT_VALUE(args[1]) < 0) {
-        is_zlib = false;
+    mp_int_t wbits = 0;
+    if (n_args > 1) {
+        wbits = MP_OBJ_SMALL_INT_VALUE(args[1]);
     }
 
-    return common_hal_zlib_decompress(args[0], is_zlib);
+    return common_hal_zlib_decompress(args[0], wbits);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(zlib_decompress_obj, 1, 3, zlib_decompress);
 
diff --git a/shared-bindings/zlib/__init__.h b/shared-bindings/zlib/__init__.h
index 232d08e294..06ffb4aef6 100644
--- a/shared-bindings/zlib/__init__.h
+++ b/shared-bindings/zlib/__init__.h
@@ -27,6 +27,6 @@
 #ifndef MICROPY_INCLUDED_SHARED_BINDINGS_ZLIB___INIT___H
 #define MICROPY_INCLUDED_SHARED_BINDINGS_ZLIB___INIT___H
 
-mp_obj_t common_hal_zlib_decompress(mp_obj_t data, bool is_zlib);
+mp_obj_t common_hal_zlib_decompress(mp_obj_t data, mp_int_t wbits);
 
 #endif  // MICROPY_INCLUDED_SHARED_BINDINGS_ZLIB___INIT___H
diff --git a/shared-module/zlib/__init__.c b/shared-module/zlib/__init__.c
index a057e6e2f7..082464fad2 100644
--- a/shared-module/zlib/__init__.c
+++ b/shared-module/zlib/__init__.c
@@ -48,7 +48,7 @@
 #define DEBUG_printf(...) (void)0
 #endif
 
-mp_obj_t common_hal_zlib_decompress(mp_obj_t data, bool is_zlib) {
+mp_obj_t common_hal_zlib_decompress(mp_obj_t data, mp_int_t wbits) {
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(data, &bufinfo, MP_BUFFER_READ);
 
@@ -66,7 +66,12 @@ mp_obj_t common_hal_zlib_decompress(mp_obj_t data, bool is_zlib) {
     decomp->source_limit = (unsigned char *)bufinfo.buf + bufinfo.len;
     int st;
 
-    if (is_zlib) {
+    if (wbits >= 16) {
+        st = uzlib_gzip_parse_header(decomp);
+        if (st < 0) {
+            goto error;
+        }
+    } else if (wbits >= 0) {
         st = uzlib_zlib_parse_header(decomp);
         if (st < 0) {
             goto error;