diff --git a/src/zeep/xsd/types/builtins.py b/src/zeep/xsd/types/builtins.py
index 206dee3d5..e3e05c657 100644
--- a/src/zeep/xsd/types/builtins.py
+++ b/src/zeep/xsd/types/builtins.py
@@ -88,6 +88,8 @@ class Decimal(BuiltinType):
 
     @check_no_collection
     def xmlvalue(self, value):
+        if isinstance(value, _Decimal):
+            return "{:f}".format(value)
         return str(value)
 
     @treat_whitespace("collapse")
diff --git a/tests/test_xsd_builtins.py b/tests/test_xsd_builtins.py
index 4c34b2ac8..a34ef8b1d 100644
--- a/tests/test_xsd_builtins.py
+++ b/tests/test_xsd_builtins.py
@@ -83,6 +83,9 @@ def test_xmlvalue(self):
         assert instance.xmlvalue(D("10.000002")) == "10.000002"
         assert instance.xmlvalue(D("10")) == "10"
         assert instance.xmlvalue(D("-10")) == "-10"
+        assert instance.xmlvalue(D("1.1E-3")) == "0.0011"
+        assert instance.xmlvalue(D("1.1E+3")) == "1100"
+        assert instance.xmlvalue(D("1.100000000000002E-3")) == "0.001100000000000002"
 
     def test_pythonvalue(self):
         instance = builtins.Decimal()