diff --git a/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py b/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
index 4eb6760a9ae..1d27e5c739b 100644
--- a/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
+++ b/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
@@ -53,9 +53,9 @@
 
 logger = logging.getLogger(__name__)
 
-MAX_NUM_ATTRIBUTES = 32
-MAX_NUM_EVENTS = 128
-MAX_NUM_LINKS = 32
+MAX_NUM_ATTRIBUTES = 1000
+MAX_NUM_EVENTS = 1000
+MAX_NUM_LINKS = 1000
 VALID_ATTR_VALUE_TYPES = (bool, str, int, float)
 
 
@@ -463,6 +463,8 @@ def _format_context(context):
     def _format_attributes(attributes):
         if isinstance(attributes, BoundedDict):
             return attributes._dict  # pylint: disable=protected-access
+        if isinstance(attributes, MappingProxyType):
+            return attributes.copy()
         return attributes
 
     @staticmethod
diff --git a/opentelemetry-sdk/tests/trace/test_trace.py b/opentelemetry-sdk/tests/trace/test_trace.py
index 92dce44e232..571fe755158 100644
--- a/opentelemetry-sdk/tests/trace/test_trace.py
+++ b/opentelemetry-sdk/tests/trace/test_trace.py
@@ -22,6 +22,7 @@
 from opentelemetry import trace as trace_api
 from opentelemetry.sdk import resources, trace
 from opentelemetry.sdk.trace import Resource, sampling
+from opentelemetry.sdk.util import ns_to_iso_str
 from opentelemetry.sdk.util.instrumentation import InstrumentationInfo
 from opentelemetry.trace.status import StatusCanonicalCode
 from opentelemetry.util import time_ns
@@ -1032,3 +1033,22 @@ def test_to_json(self):
             span.to_json(indent=None),
             '{"name": "span-name", "context": {"trace_id": "0x000000000000000000000000deadbeef", "span_id": "0x00000000deadbef0", "trace_state": "{}"}, "kind": "SpanKind.INTERNAL", "parent_id": null, "start_time": null, "end_time": null, "attributes": {}, "events": [], "links": [], "resource": {}}',
         )
+
+    def test_attributes_to_json(self):
+        context = trace_api.SpanContext(
+            trace_id=0x000000000000000000000000DEADBEEF,
+            span_id=0x00000000DEADBEF0,
+            is_remote=False,
+            trace_flags=trace_api.TraceFlags(trace_api.TraceFlags.SAMPLED),
+        )
+        span = trace._Span("span-name", context)
+        span.resource = Resource({})
+        span.set_attribute("key", "value")
+        span.add_event("event", {"key2": "value2"}, 123)
+        date_str = ns_to_iso_str(123)
+        self.assertEqual(
+            span.to_json(indent=None),
+            '{"name": "span-name", "context": {"trace_id": "0x000000000000000000000000deadbeef", "span_id": "0x00000000deadbef0", "trace_state": "{}"}, "kind": "SpanKind.INTERNAL", "parent_id": null, "start_time": null, "end_time": null, "attributes": {"key": "value"}, "events": [{"name": "event", "timestamp": "'
+            + date_str
+            + '", "attributes": {"key2": "value2"}}], "links": [], "resource": {}}',
+        )