diff --git a/modules/account_invoice/invoice.py b/modules/account_invoice/invoice.py
index 90fc0f805f..e1260220c4 100644
--- a/modules/account_invoice/invoice.py
+++ b/modules/account_invoice/invoice.py
@@ -782,7 +782,7 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin):
         invoice_query = Rule.query_get('account.invoice')
         Operator = fields.SQL_OPERATORS[operator]
         # SQLite uses float for sum
-        if backend.name == 'sqlite':
+        if value is not None and backend.name == 'sqlite':
             value = float(value)
 
         union = (line.join(invoice, condition=(invoice.id == line.invoice)
@@ -818,7 +818,7 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin):
         invoice_query = Rule.query_get('account.invoice')
         Operator = fields.SQL_OPERATORS[operator]
         # SQLite uses float for sum
-        if backend.name == 'sqlite':
+        if value is not None and backend.name == 'sqlite':
             value = float(value)
 
         query = line.join(invoice,
@@ -847,7 +847,7 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin):
         invoice_query = Rule.query_get('account.invoice')
         Operator = fields.SQL_OPERATORS[operator]
         # SQLite uses float for sum
-        if backend.name == 'sqlite':
+        if value is not None and backend.name == 'sqlite':
             value = float(value)
 
         query = tax.select(tax.invoice,