diff --git a/src/resources.py b/src/resources.py
index f77ce4d..654191c 100644
--- a/src/resources.py
+++ b/src/resources.py
@@ -159,36 +159,40 @@ class SampleResource(Resource):
             filters = []
             try:
                 first = int(request.args.get('first'))
+            except (ValueError, TypeError):
+                first = None
+            else:
                 filters.append(
                     SampleMetadata.id >= first
                 )
-            except ValueError:
-                first = None
 
             try:
                 after = datetime.fromisoformat(request.args.get('after'))
+            except (ValueError, TypeError):
+                after = None
+            else:
                 filters.append(
                     SampleMetadata.timestamp > after
                 )
-            except ValueError:
-                after = None
 
             try:
                 before = datetime.fromisoformat(request.args.get('after'))
+            except (ValueError, TypeError):
+                before = None
+            else:
                 filters.append(
                     SampleMetadata.timestamp < before
                 )
-            except ValueError:
-                before = None
 
             if filters:
                 query = query.filter(db.and_(*filters))
 
             try:
                 limit = int(request.args.get('limit'))
-                query = query.limit(limit)
-            except ValueError:
+            except (ValueError, TypeError):
                 limit = None
+            else:
+                query = query.limit(limit)
 
         ## Run query ##
         count = "count" in request.args.get