diff --git a/django/db/backends/schema.py b/django/db/backends/schema.py
index 64ba5b0740..4fc6601dfd 100644
--- a/django/db/backends/schema.py
+++ b/django/db/backends/schema.py
@@ -93,7 +93,11 @@ class BaseDatabaseSchemaEditor(object):
         # Log the command we're running, then run it
         logger.debug("%s; (params %r)" % (sql, params))
         if self.collect_sql:
-            self.collected_sql.append((sql % tuple(map(self.quote_value, params))) + ";")
+            ending = "" if sql.endswith(";") else ";"
+            if params is not None:
+                self.collected_sql.append((sql % tuple(map(self.quote_value, params))) + ending)
+            else:
+                self.collected_sql.append(sql + ending)
         else:
             with self.connection.cursor() as cursor:
                 cursor.execute(sql, params)
diff --git a/docs/releases/1.7.2.txt b/docs/releases/1.7.2.txt
index 9ed58bb217..c01dca9f58 100644
--- a/docs/releases/1.7.2.txt
+++ b/docs/releases/1.7.2.txt
@@ -91,3 +91,6 @@ Bugfixes
   the error message for cyclic dependencies much more helpful.
 
 * Added missing ``index_together`` handling for SQLite (:ticket:`23880`).
+
+* Fixed a crash when ``RunSQL`` SQL content was collected by the schema editor,
+  typically when using ``sqlmigrate`` (:ticket:`23909`).
diff --git a/tests/migrations/test_operations.py b/tests/migrations/test_operations.py
index 05e0f22696..5f4dc553a2 100644
--- a/tests/migrations/test_operations.py
+++ b/tests/migrations/test_operations.py
@@ -1219,6 +1219,12 @@ class OperationTests(OperationTestBase):
         self.assertEqual(len(new_state.models["test_runsql", "somethingelse"].fields), 1)
         # Make sure there's no table
         self.assertTableNotExists("i_love_ponies")
+        # Test SQL collection
+        with connection.schema_editor(collect_sql=True) as editor:
+            operation.database_forwards("test_runsql", editor, project_state, new_state)
+            self.assertIn("LIKE '%%ponies';", "\n".join(editor.collected_sql))
+            operation.database_backwards("test_runsql", editor, project_state, new_state)
+            self.assertIn("LIKE '%%Ponies%%';", "\n".join(editor.collected_sql))
         # Test the database alteration
         with connection.schema_editor() as editor:
             operation.database_forwards("test_runsql", editor, project_state, new_state)