diff --git a/ihatemoney/web.py b/ihatemoney/web.py
index baacff47..576d6e10 100644
--- a/ihatemoney/web.py
+++ b/ihatemoney/web.py
@@ -414,17 +414,30 @@ def edit_project():
 
     # Edit form
     if edit_form.validate_on_submit():
+        old_currency = g.project.default_currency
         project = edit_form.update(g.project)
         # Update converted currency
-        if project.default_currency != CurrencyConverter.no_currency:
+        if project.default_currency != old_currency:
             for bill in project.get_bills():
+                if bill.original_currency == project.default_currency:
+                    continue
 
-                if bill.original_currency == CurrencyConverter.no_currency:
-                    bill.original_currency = project.default_currency
-
-                bill.converted_amount = CurrencyConverter().exchange_currency(
-                    bill.amount, bill.original_currency, project.default_currency
-                )
+                if project.default_currency == CurrencyConverter.no_currency:
+                    # Use old currency before stripping
+                    bill.converted_amount = CurrencyConverter().exchange_currency(
+                        bill.amount, bill.original_currency, old_currency
+                    )
+                    # Strip currency
+                    bill.amount = bill.converted_amount
+                    bill.original_currency = CurrencyConverter.no_currency
+                else:
+                    # Switch to new currency for everyone
+                    bill.converted_amount = CurrencyConverter().exchange_currency(
+                        bill.amount, bill.original_currency, project.default_currency
+                    )
+                    # Add the currency for previously un-currency-ied
+                    if bill.original_currency == CurrencyConverter.no_currency:
+                        bill.original_currency = project.default_currency
                 db.session.add(bill)
 
         db.session.add(project)