diff --git a/bindings/python/dlite-entity-python.i b/bindings/python/dlite-entity-python.i
index 7a572c2ef..1d7511ec6 100644
--- a/bindings/python/dlite-entity-python.i
+++ b/bindings/python/dlite-entity-python.i
@@ -404,6 +404,7 @@ def get_instance(
         # Allow metaid to be an Instance
         if isinstance(metaid, Instance):
             metaid = metaid.uri
+        errclr()  # Clear internal error before calling Instance()
         inst = Instance(
             metaid=metaid, dims=dimensions, id=id,
             dimensions=(), properties=()  # arrays must not be None
@@ -488,6 +489,7 @@ def get_instance(
                 metaid=metaid
             )
         else:
+            errclr()  # Clear internal error before calling Instance()
             inst = Instance(
                 url=url, metaid=metaid,
                 dims=(), dimensions=(), properties=()  # arrays
@@ -502,6 +504,7 @@ def get_instance(
         If `metaid` is provided, the instance is tried mapped to this
         metadata before it is returned.
         """
+        errclr()  # Clear internal error before calling Instance()
         inst = Instance(
             storage=storage, id=id, metaid=metaid,
             dims=(), dimensions=(), properties=()  # arrays
@@ -519,6 +522,7 @@ def get_instance(
         from dlite.options import make_query
         if options and not isinstance(options, str):
             options = make_query(options)
+        errclr()  # Clear internal error before calling Instance()
         inst = Instance(
             driver=driver, location=str(location), options=options, id=id,
             metaid=metaid,
@@ -529,6 +533,7 @@ def get_instance(
     @classmethod
     def from_json(cls, jsoninput, id=None, metaid=None):
         """Load the instance from json input."""
+        errclr()  # Clear internal error before calling Instance()
         inst = Instance(
             jsoninput=jsoninput, id=id, metaid=metaid,
             dims=(), dimensions=(), properties=()  # arrays
@@ -538,6 +543,7 @@ def get_instance(
     @classmethod
     def from_bson(cls, bsoninput):
         """Load the instance from bson input."""
+        errclr()  # Clear internal error before calling Instance()
         inst = Instance(
             bsoninput=bsoninput,
             dims=(), dimensions=(), properties=()  # arrays
@@ -593,6 +599,7 @@ def get_instance(
         """Create a new metadata entity (instance of entity schema) casted
         to an instance.
         """
+        errclr()  # Clear internal error before calling Instance()
         inst = Instance(
             uri=uri, dimensions=dimensions, properties=properties,
             description=description,
@@ -614,6 +621,7 @@ def get_instance(
             meta = get_instance(metaid)
             dimensions = [dimensions[dim.name]
                           for dim in meta.properties['dimensions']]
+        errclr()  # Clear internal error before calling Instance()
         inst = Instance(
             metaid=metaid, dims=dimensions, id=id,
             dimensions=(), properties=()  # arrays must not be None
@@ -630,10 +638,12 @@ def get_instance(
         warnings.warn(
             "create_from_url() is deprecated, use from_url() instead.",
             DeprecationWarning, stacklevel=2)
-        return Instance(
+        errclr()  # Clear internal error before calling Instance()
+        inst = Instance(
             url=url, metaid=metaid,
             dims=(), dimensions=(), properties=()  # arrays
         )
+        return instance_cast(inst)
 
     @classmethod
     def create_from_storage(cls, storage, id=None, metaid=None):
@@ -646,6 +656,7 @@ def get_instance(
         warnings.warn(
             "create_from_storage() is deprecated, use from_storage() instead.",
             DeprecationWarning, stacklevel=2)
+        errclr()  # Clear internal error before calling Instance()
         inst = Instance(
             storage=storage, id=id, metaid=metaid,
             dims=(), dimensions=(), properties=()  # arrays
@@ -664,12 +675,30 @@ def get_instance(
         from dlite.options import make_query
         if options and not isinstance(options, str):
             options = make_query(options)
+        errclr()  # Clear internal error before calling Instance()
         inst = Instance(
             driver=driver, location=str(location), options=options, id=id,
             dims=(), dimensions=(), properties=()  # arrays
         )
         return instance_cast(inst)
 
+    @classmethod
+    def get_uuids(cls, driver, location, options=None, pattern=None):
+        """Returns a iterator over matching UUIDs in storage.
+
+          Arguments:
+              driver: Name of storage plugin for data parsing.
+              location: Location of resource.  Typically a URL or file path.
+              options: Options passed to the protocol and driver plugins.
+              pattern: A glob pattern matching metadata UUIDs.  If given,
+                  only matching UUIDs will be returned.
+
+          Return:
+              Iterator over all matching UUIDs in storage.
+        """
+        with Storage(driver, location, options=options) as s:
+             return s.get_uuids(pattern=pattern)
+
     def save(self, *dest, location=None, options=None):
         """Saves this instance to url or storage.
 
diff --git a/bindings/python/scripts/dlite-validate b/bindings/python/scripts/dlite-validate
index 8a2635e34..b89821fb0 100644
--- a/bindings/python/scripts/dlite-validate
+++ b/bindings/python/scripts/dlite-validate
@@ -10,7 +10,7 @@ from pathlib import Path
 import dlite
 
 
-def parse(url, driver=None, options=None, id=None):
+def parse(url, driver=None, options="mode=r", id=None):
     """Loads an instance from storage.
 
     Arguments:
diff --git a/bindings/python/tests/test_entity.py b/bindings/python/tests/test_entity.py
index 297b0e336..fe3ad2a6d 100644
--- a/bindings/python/tests/test_entity.py
+++ b/bindings/python/tests/test_entity.py
@@ -343,10 +343,37 @@
     assert item.q.f.m.tolist() == [0., 1., 0.001]
     assert item.q.f.to("1/hour").m.tolist() == [0, 3600, 3.6]
 
-    
+
 # For issue #750 - test instance_cast()
 with raises(dlite.DLiteTypeError):
     dlite.instance_cast(inst, dlite.Metadata)
 castinst = dlite.instance_cast(inst.meta, dlite.Instance)
 assert type(castinst) == dlite.Instance
 assert type(dlite.instance_cast(castinst)) == dlite.Metadata
+
+
+# Test storage query
+uuids = {
+    '850637b9-1d21-573c-91b6-477530e4bf58',
+    '020e411b-f349-5689-8657-f82b709369c3',
+    '570611f5-96b3-5b0d-90ad-f3a4c19a78b2',
+    '5e378ac7-83c9-5d77-ab20-b5bb32c695da',
+    'e5efe084-27f2-5fec-9b1c-fa1a692e1434',
+}
+with dlite.Storage("json", indir / "test_ref_type.json") as s:
+    assert set(s.get_uuids()) == uuids
+    assert set(s.get_uuids("http://onto-ns.com/meta/0.3/EntitySchema")) == uuids
+    assert s.get_uuids("xxx") == []
+assert set(
+    dlite.Instance.get_uuids("json", indir / "test_ref_type.json")
+) == uuids
+assert set(
+    dlite.Instance.get_uuids(
+        "json", indir / "test_ref_type.json",
+        pattern="http://onto-ns.com/meta/0.3/EntitySchema",
+    )
+) == uuids
+assert dlite.Instance.get_uuids(
+    "json", indir / "test_ref_type.json",
+    pattern="xxx",
+) == []
diff --git a/bindings/python/tests/test_storage.py b/bindings/python/tests/test_storage.py
index a986b0bac..0999353ba 100755
--- a/bindings/python/tests/test_storage.py
+++ b/bindings/python/tests/test_storage.py
@@ -244,6 +244,7 @@
 
 
 # Test plugin that only defines to_bytes() and from_bytes()
-#print("===================================")
-#dlite.Storage.plugin_help("testbuff")
-#buf = inst.to_bytes("bufftest")
+txt = dlite.Storage.plugin_help("bufftest")
+assert txt == "Test plugin that represents instances as byte-encoded json."
+buf = inst.to_bytes("bufftest")
+assert buf == str(inst).encode()
diff --git a/src/dlite-json.c b/src/dlite-json.c
index 3993f2b75..bbb3bfcb4 100644
--- a/src/dlite-json.c
+++ b/src/dlite-json.c
@@ -1053,6 +1053,7 @@ struct _DLiteJsonIter {
   const jsmntok_t *t;     /*!< Pointer to current token */
   unsigned int n;         /*!< Current token number */
   unsigned int size;      /*!< Size of the root object */
+  //char *metaid;           /*!< Metadata id to match */
   char metauuid[DLITE_UUID_LENGTH+1];  /*!< UUID of metadata */
 };
 
@@ -1099,7 +1100,7 @@ static const jsmntok_t *nexttok(DLiteJsonIter *iter, int *length)
 DLiteJsonIter *dlite_json_iter_create(const char *src, int length,
                                       const char *metaid)
 {
-  int r, ok=0;
+  int r;
   DLiteJsonIter *iter=NULL;
   jsmn_parser parser;
 
@@ -1116,10 +1117,10 @@ DLiteJsonIter *dlite_json_iter_create(const char *src, int length,
   iter->size = iter->tokens->size;
   if (metaid && dlite_get_uuid(iter->metauuid, metaid) < 0) goto fail;
 
-  ok=1;
- fail:
-  if (!ok) dlite_json_iter_free(iter);
   return iter;
+ fail:
+  if (iter) dlite_json_iter_free(iter);
+  return NULL;
 }
 
 /*
@@ -1308,11 +1309,15 @@ const char *dlite_jstore_iter_next(DLiteJStoreIter *iter)
     if (iter->metauuid[0]) {
       char metauuid[DLITE_UUID_LENGTH+1];
       const char *val = jstore_get(js, iid);
+      int r;
 
       jsmn_init(&parser);
-      if (jsmn_parse_alloc(&parser, val, strlen(val),
-                           &iter->tokens, &iter->ntokens) < 0) {
-        err(dliteParseError, "invalid json input: \"%s\"", val);
+      if ((r = jsmn_parse_alloc(&parser, val, strlen(val),
+                                &iter->tokens, &iter->ntokens)) < 0) {
+        if (r == JSMN_ERROR_INVAL)
+          err(dliteParseError, "invalid json input: \"%s\"", val);
+        else
+          err(dliteParseError, "json parse error: \"%s\"", jsmn_strerror(r));
         continue;
       }
       if (get_meta_uuid(metauuid, val, iter->tokens)) {
diff --git a/src/utils/jsmn.h b/src/utils/jsmn.h
index dca2bb592..a3dbbabdf 100644
--- a/src/utils/jsmn.h
+++ b/src/utils/jsmn.h
@@ -87,7 +87,7 @@ typedef struct jsmn_parser {
 } jsmn_parser;
 
 /**
- * Create JSON parser over an array of tokens
+ * Initializes a JSON parser.
  */
 JSMN_API void jsmn_init(jsmn_parser *parser);
 
diff --git a/src/utils/jsmnx.c b/src/utils/jsmnx.c
index 67a5e490d..6fad361d6 100644
--- a/src/utils/jsmnx.c
+++ b/src/utils/jsmnx.c
@@ -24,13 +24,15 @@
   if it is too small.  `num_tokens_ptr` should point to the number of
   allocated tokens.
 
-  Returns JSMN_ERROR_NOMEM on allocation error.
+  Returns number of tokens used by the parser or one of the following error
+  codes on error:
+    - JSMN_ERROR_NOMEM on allocation error.
+    - JSMN_INVAL on invalid character inside json string.
  */
 int jsmn_parse_alloc(jsmn_parser *parser, const char *js, const size_t len,
                      jsmntok_t **tokens_ptr, unsigned int *num_tokens_ptr)
 {
   int n, n_save;
-  unsigned int saved_pos;
   jsmntok_t *t=NULL;
   (void) n_save;  // avoid unused parameter error when assert is turned off
   assert(tokens_ptr);
@@ -38,28 +40,30 @@ int jsmn_parse_alloc(jsmn_parser *parser, const char *js, const size_t len,
   if (!*num_tokens_ptr) *tokens_ptr = NULL;
   if (!*tokens_ptr) *num_tokens_ptr = 0;
 
-  saved_pos = parser->pos;
-
   if (!*tokens_ptr) {
-    if ((n = jsmn_parse(parser, js, len, NULL, 0)) < 0) goto fail;
+    jsmn_parser tmp_parser;
+    jsmn_init(&tmp_parser);
+    if ((n = jsmn_parse(&tmp_parser, js, len, NULL, 0)) < 0) goto fail;
     /* FIXME: there seems to be an issue with the dlite_json_check() that
        looks post the last allocated token. Allocating `n+1` tokens is a
        workaround to avoid memory issues. */
     if (!(t = calloc(n+1, sizeof(jsmntok_t)))) return JSMN_ERROR_NOMEM;
   } else {
+    jsmn_parser tmp_parser, saved_parser;
+    memcpy(&saved_parser, parser, sizeof(saved_parser));
     n = jsmn_parse(parser, js, len, *tokens_ptr, *num_tokens_ptr);
     if (n >= 0) return n;
     if (n != JSMN_ERROR_NOMEM) goto fail;
-    if (!(t = realloc(*tokens_ptr, n*sizeof(jsmntok_t))))
+    memcpy(parser, &saved_parser, sizeof(saved_parser));
+    jsmn_init(&tmp_parser);
+    if ((n = jsmn_parse(&tmp_parser, js, len, NULL, 0)) < 0) goto fail;
+    if (!(t = realloc(*tokens_ptr, (n+1)*sizeof(jsmntok_t))))
       return JSMN_ERROR_NOMEM;
   }
   *tokens_ptr = t;
   *num_tokens_ptr = n;
   n_save = n;
 
-  /* TODO: Instead of resetting the parser, we should continue after
-     reallocation */
-  parser->pos = saved_pos;
   if ((n = jsmn_parse(parser, js, len, t, n)) < 0) goto fail;
   assert(n == n_save);
   return n;
diff --git a/src/utils/jsmnx.h b/src/utils/jsmnx.h
index 077e605c8..e596d6d2c 100644
--- a/src/utils/jsmnx.h
+++ b/src/utils/jsmnx.h
@@ -43,9 +43,7 @@ void jsmn_init(jsmn_parser *parser);
 
 
 /**
- * Run JSON parser.
- *
- * It parses a JSON data string into and array of tokens, each
+ * Parse a JSON data string into and array of tokens, each
  * describing a single JSON object.
  *
  * Arguments
@@ -60,8 +58,9 @@ void jsmn_init(jsmn_parser *parser);
  * Returns
  * -------
  * On success, it returns the number of tokens actually used by the parser.
- * On error, one of the following (negative) codes is returned:
+ * If `tokens` is NULL, the number of needed will be returned.
  *
+ * On error, one of the following (negative) codes is returned:
  *  - JSMN_ERROR_INVAL: bad token, JSON string is corrupted
  *  - JSMN_ERROR_NOMEM: not enough tokens, JSON string is too large
  *  - JSMN_ERROR_PART:  JSON string is too short, expecting more JSON data