diff --git a/django/db/models/functions/comparison.py b/django/db/models/functions/comparison.py
index 6c0b33bdcc..24c3c4b4b8 100644
--- a/django/db/models/functions/comparison.py
+++ b/django/db/models/functions/comparison.py
@@ -53,14 +53,10 @@ class Coalesce(Func):
         # Oracle prohibits mixing TextField (NCLOB) and CharField (NVARCHAR2),
         # so convert all fields to NCLOB when that type is expected.
         if self.output_field.get_internal_type() == 'TextField':
-            class ToNCLOB(Func):
-                function = 'TO_NCLOB'
-
-            expressions = [
-                ToNCLOB(expression) for expression in self.get_source_expressions()
-            ]
             clone = self.copy()
-            clone.set_source_expressions(expressions)
+            clone.set_source_expressions([
+                Func(expression, function='TO_NCLOB') for expression in self.get_source_expressions()
+            ])
             return super(Coalesce, clone).as_sql(compiler, connection, **extra_context)
         return self.as_sql(compiler, connection, **extra_context)
 
diff --git a/django/db/models/functions/text.py b/django/db/models/functions/text.py
index 9624f0911f..6216cbf6e6 100644
--- a/django/db/models/functions/text.py
+++ b/django/db/models/functions/text.py
@@ -67,10 +67,9 @@ class ConcatPair(Func):
     def coalesce(self):
         # null on either side results in null for expression, wrap with coalesce
         c = self.copy()
-        expressions = [
+        c.set_source_expressions([
             Coalesce(expression, Value('')) for expression in c.get_source_expressions()
-        ]
-        c.set_source_expressions(expressions)
+        ])
         return c