diff --git a/sheetsync/sheetsync/main.py b/sheetsync/sheetsync/main.py
index 0d4b889..ed5a80d 100644
--- a/sheetsync/sheetsync/main.py
+++ b/sheetsync/sheetsync/main.py
@@ -112,7 +112,7 @@ class SheetSync(object):
 				db_rows = self.get_db_rows()
 				seen = set()
 
-				is_full, sheet_rows = self.middleware.get_rows()
+				worksheets, sheet_rows = self.middleware.get_rows()
 				for row in sheet_rows:
 					if row['id'] in seen:
 						self.logger.error("Duplicate id {}, skipping".format(row['id']))
@@ -120,16 +120,14 @@ class SheetSync(object):
 					seen.add(row['id'])
 					self.sync_row(row, db_rows.get(row['id']))
 
-				if is_full:
-					# Find rows that were not in the sheet.
-					# Only do this if we did a full sync, otherwise things might be missing
-					# simply because they're in a worksheet we didn't sync.
-					missing = [
-						r for id, r in db_rows.items()
-						if id not in seen
-					]
-					for db_row in missing:
-						self.sync_row(None, db_row)
+				# Find rows that were not in the sheet, that were expected to be in that sheet.
+				missing = [
+					r for id, r in db_rows.items()
+					if id not in seen
+					and self.middleware.row_was_expected(r, worksheets)
+				]
+				for db_row in missing:
+					self.sync_row(None, db_row)
 
 			except Exception as e:
 				# for HTTPErrors, http response body includes the more detailed error
diff --git a/sheetsync/sheetsync/middleware.py b/sheetsync/sheetsync/middleware.py
index bc65303..4797841 100644
--- a/sheetsync/sheetsync/middleware.py
+++ b/sheetsync/sheetsync/middleware.py
@@ -13,12 +13,20 @@ class Middleware:
 				is still required.
 			_parse_errors: A list of error messages encountered when parsing, to be surfaced to the
 				user if possible.
-		In addition to the list of dicts, should return an "is_full" boolean which is True
-		if all rows were fetched or False if only some subset was fetched (eg. for quota management reasons).
-		Returns (is_full, rows).
+		In addition to the list of dicts, should return a list of worksheets fetched from,
+		which is then passed to row_was_expected().
+		Returns (worksheets, rows).
 		"""
 		raise NotImplementedError
 
+	def row_was_expected(self, db_row, worksheets):
+		"""Given a database row and list of worksheets from get_rows(), return whether
+		the given row should have been present in the returned rows, ie. if we expected
+		to find it on one of those worksheets."""
+		# Default to the common case, which is that we always return all data
+		# so the row should always be expected.
+		return True
+
 	def write_value(self, row, key, value):
 		"""Write key=value to the given row. Takes the full row object so any identifying info
 		can be read from it as needed."""
diff --git a/sheetsync/sheetsync/sheets.py b/sheetsync/sheetsync/sheets.py
index 4291b73..ef8733e 100644
--- a/sheetsync/sheetsync/sheets.py
+++ b/sheetsync/sheetsync/sheets.py
@@ -103,8 +103,7 @@ class SheetsMiddleware(Middleware):
 					self.write_id(row)
 
 				all_rows.append(row)
-		is_full = sorted(worksheets) == list(self.worksheets.keys())
-		return is_full, all_rows
+		return worksheets, all_rows
 
 	def row_is_non_empty(self, row):
 		"""Returns True if row is considered to be non-empty and should have an id assigned."""
@@ -218,6 +217,11 @@ class SheetsPlaylistsMiddleware(SheetsMiddleware):
 		"show_in_description": ENCODE_CHECKMARK,
 	}
 
+	def row_was_expected(self, db_row, worksheets):
+		# Database does not record a worksheet for playlists, we assume there's only one
+		# sheet and so it should always be there.
+		return True
+
 	def row_is_non_empty(self, row):
 		return row["tags"] is not None
 
@@ -284,6 +288,9 @@ class SheetsEventsMiddleware(SheetsMiddleware):
 		bustime = common.dt_to_bustime(self.bustime_start, value)
 		return common.format_bustime(bustime, round="minute")
 
+	def row_was_expected(self, db_row, worksheets):
+		return db_row.sheet_name in worksheets
+
 	def row_is_non_empty(self, row):
 		return any(row[col] for col in ["event_start", "description"])
 
diff --git a/sheetsync/sheetsync/streamlog.py b/sheetsync/sheetsync/streamlog.py
index 9db2eb7..928a8f6 100644
--- a/sheetsync/sheetsync/streamlog.py
+++ b/sheetsync/sheetsync/streamlog.py
@@ -71,7 +71,7 @@ class StreamLogPlaylistsMiddleware(Middleware):
 				"first_event_id": None, # TODO missing in StreamLog
 				"last_event_id": None, # TODO missing in StreamLog
 			})
-		return True, rows
+		return None, rows
 
 	# writing intentionally not implemented
 
@@ -124,8 +124,8 @@ class StreamLogEventsMiddleware(Middleware):
 			# Malformed rows can be skipped, represented as a None result
 			if row is not None:
 				all_rows.append(row)
-		# There's no worksheet concept here so we always return a full sync.
-		return True, all_rows
+		# There's no worksheet concept here so just return None for worksheets.
+		return None, all_rows
 
 	def parse_row(self, row):
 		output = {}