diff --git a/datadog_lambda/cold_start.py b/datadog_lambda/cold_start.py
index fdb43b81..a10a2ad7 100644
--- a/datadog_lambda/cold_start.py
+++ b/datadog_lambda/cold_start.py
@@ -134,14 +134,16 @@ def __init__(
         self,
         tracer,
         function_name,
-        cold_start_span_finish_time_ns,
+        current_span_start_time_ns,
         trace_ctx,
         min_duration_ms: int,
-        ignored_libs: List[str] = [],
+        ignored_libs: List[str] = None,
     ):
+        if ignored_libs is None:
+            ignored_libs = []
         self._tracer = tracer
         self.function_name = function_name
-        self.cold_start_span_finish_time_ns = cold_start_span_finish_time_ns
+        self.current_span_start_time_ns = current_span_start_time_ns
         self.min_duration_ms = min_duration_ms
         self.trace_ctx = trace_ctx
         self.ignored_libs = ignored_libs
@@ -151,11 +153,14 @@ def trace(self, root_nodes: List[ImportNode] = root_nodes):
         if not root_nodes:
             return
         cold_start_span_start_time_ns = root_nodes[0].start_time_ns
+        cold_start_span_end_time_ns = min(
+            root_nodes[-1].end_time_ns, self.current_span_start_time_ns
+        )
         cold_start_span = self.create_cold_start_span(cold_start_span_start_time_ns)
         while root_nodes:
             root_node = root_nodes.pop()
             self.trace_tree(root_node, cold_start_span)
-        self.finish_span(cold_start_span, self.cold_start_span_finish_time_ns)
+        self.finish_span(cold_start_span, cold_start_span_end_time_ns)
 
     def trace_tree(self, import_node: ImportNode, parent_span):
         if (
diff --git a/datadog_lambda/tracing.py b/datadog_lambda/tracing.py
index 67836e46..7879697e 100644
--- a/datadog_lambda/tracing.py
+++ b/datadog_lambda/tracing.py
@@ -385,7 +385,7 @@ def is_authorizer_response(response) -> bool:
             and response["principalId"]
             and response["policyDocument"]
         )
-    except KeyError:
+    except (KeyError, AttributeError):
         pass
     except Exception as e:
         logger.debug("unknown error while checking is_authorizer_response %s", e)
diff --git a/scripts/build_layers.sh b/scripts/build_layers.sh
index 0bf67f49..e1bd557e 100755
--- a/scripts/build_layers.sh
+++ b/scripts/build_layers.sh
@@ -68,7 +68,7 @@ mkdir $LAYER_DIR
 
 for python_version in "${PYTHON_VERSIONS[@]}"
 do
-    if [ "$python_version" == "3.8" ] || [ "$python_version" == "3.9" ]; then
+    if [ "$python_version" != "3.7" ]; then
         echo "Building layer for Python ${python_version} arch=arm64"
         docker_build_zip ${python_version} $LAYER_DIR/${LAYER_FILES_PREFIX}-arm64-${python_version}.zip arm64
     fi