diff --git a/tests/form_pages/test_computed_field.py b/tests/form_pages/test_computed_field.py
index 6cefa3cb8..9300272f8 100644
--- a/tests/form_pages/test_computed_field.py
+++ b/tests/form_pages/test_computed_field.py
@@ -1,4 +1,5 @@
 import datetime
+import decimal
 
 import pytest
 from django.utils.timezone import make_aware
@@ -330,6 +331,36 @@ def test_computed_field_complex_data(pub, http_requests):
     assert formdata.data['1'] == {'foo': 'bar'}
 
 
+def test_computed_field_decimal_data(pub, http_requests):
+    FormDef.wipe()
+
+    formdef = FormDef()
+    formdef.name = 'test'
+    formdef.fields = [
+        fields.ComputedField(
+            id='1',
+            label='computed',
+            varname='computed',
+            value_template='{{ "123.45"|decimal }}',
+            freeze_on_initial_value=True,
+        ),
+        fields.CommentField(id='2', label='X{{form_var_computed}}Y', type='comment'),
+    ]
+    formdef.store()
+    formdef.data_class().wipe()
+
+    resp = get_app(pub).get('/test/')
+    assert 'X123.45Y' in resp.text
+    resp = resp.forms[0].submit('submit')  # -> validation
+    resp = resp.forms[0].submit('submit').follow()  # -> submit
+    assert 'The form has been recorded' in resp.text
+    assert formdef.data_class().count() == 1
+    formdata = formdef.data_class().select()[0]
+    # pickle storage keeps the typed data but postgresql storage has to convert
+    # it to stringfor json storage, hence the casting here:
+    assert decimal.Decimal(formdata.data['1']) == decimal.Decimal('123.45')
+
+
 def test_computed_field_usage_in_live_data(pub, http_requests):
     FormDef.wipe()
 
diff --git a/wcs/sql.py b/wcs/sql.py
index 529e3d15d..e3fee9037 100644
--- a/wcs/sql.py
+++ b/wcs/sql.py
@@ -17,6 +17,7 @@
 import copy
 import datetime
 import io
+import json
 import re
 import time
 import unicodedata
@@ -47,7 +48,7 @@ from wcs.qommon import PICKLE_KWARGS, force_str
 from . import qommon
 from .publisher import UnpicklerClass
 from .qommon import _, get_cfg
-from .qommon.misc import strftime
+from .qommon.misc import JSONEncoder, strftime
 from .qommon.storage import _take, deep_bytes2str
 from .qommon.storage import parse_clause as parse_storage_clause
 from .qommon.substitution import invalidate_substitution_cache
@@ -1700,7 +1701,7 @@ class SqlMixin:
                     if value is not None:
                         # embed value in a dict, so it's never necessary to cast the
                         # value for postgresql
-                        value = {'data': value, '@type': 'computed-data'}
+                        value = {'data': json.loads(JSONEncoder().encode(value)), '@type': 'computed-data'}
                 elif sql_type == 'varchar':
                     assert isinstance(value, str)
                 elif sql_type == 'date':