diff --git a/pythonfmu/default_experiment.py b/pythonfmu/default_experiment.py
index 817cf08..c0aabb2 100644
--- a/pythonfmu/default_experiment.py
+++ b/pythonfmu/default_experiment.py
@@ -1,6 +1,7 @@
 class DefaultExperiment:
 
-    def __init__(self, start_time: float = None, stop_time: float = None, tolerance: float = None):
+    def __init__(self, start_time: float = None, stop_time: float = None, step_size: float = None, tolerance: float = None):
         self.start_time = start_time
         self.stop_time = stop_time
+        self.step_size = step_size
         self.tolerance = tolerance
diff --git a/pythonfmu/fmi2slave.py b/pythonfmu/fmi2slave.py
index 8780829..d06a50d 100644
--- a/pythonfmu/fmi2slave.py
+++ b/pythonfmu/fmi2slave.py
@@ -110,6 +110,18 @@ def to_xml(self, model_options: Dict[str, str] = dict()) -> Element:
                     )
                 )
 
+        if self.default_experiment is not None:
+            attrib = dict()
+            if self.default_experiment.start_time is not None:
+                attrib["startTime"] = str(self.default_experiment.start_time)
+            if self.default_experiment.stop_time is not None:
+                attrib["stopTime"] = str(self.default_experiment.stop_time)
+            if self.default_experiment.step_size is not None:
+                attrib["stepSize"] = str(self.default_experiment.step_size)
+            if self.default_experiment.tolerance is not None:
+                attrib["tolerance"] = str(self.default_experiment.tolerance)
+            SubElement(root, "DefaultExperiment", attrib)
+
         variables = SubElement(root, "ModelVariables")
         for v in self.vars.values():
             if ScalarVariable.requires_start(v):
@@ -127,16 +139,6 @@ def to_xml(self, model_options: Dict[str, str] = dict()) -> Element:
                 if v.causality == Fmi2Causality.output:
                     SubElement(outputs_node, "Unknown", attrib=dict(index=str(i + 1)))
 
-        if self.default_experiment is not None:
-            attrib = dict()
-            if self.default_experiment.start_time is not None:
-                attrib["startTime"] = self.default_experiment.start_time
-            if self.default_experiment.stop_time is not None:
-                attrib["stopTime"] = self.default_experiment.stop_time
-            if self.default_experiment.tolerance is not None:
-                attrib["tolerance"] = self.default_experiment.tolerance
-            SubElement(root, "DefaultExperiment", attrib)
-
         return root
 
     def __apply_start_value(self, var: ScalarVariable):
diff --git a/pythonfmu/tests/slaves/pythonslave_read_file.py b/pythonfmu/tests/slaves/pythonslave_read_file.py
index 7db110b..b07b8b9 100644
--- a/pythonfmu/tests/slaves/pythonslave_read_file.py
+++ b/pythonfmu/tests/slaves/pythonslave_read_file.py
@@ -1,8 +1,10 @@
-from pythonfmu.fmi2slave import Fmi2Slave, Fmi2Causality, Fmi2Variability, String
+from pythonfmu.fmi2slave import Fmi2Slave, Fmi2Causality, Fmi2Variability, String, DefaultExperiment
 
 
 class PythonSlaveReadFile(Fmi2Slave):
 
+    default_experiment = DefaultExperiment(start_time=0)
+
     def __init__(self, **kwargs):
         super().__init__(**kwargs)
 
diff --git a/pythonfmu/tests/test_default_experiment.py b/pythonfmu/tests/test_default_experiment.py
new file mode 100644
index 0000000..7c5a1df
--- /dev/null
+++ b/pythonfmu/tests/test_default_experiment.py
@@ -0,0 +1,17 @@
+import pytest
+from pathlib import Path
+
+from pythonfmu.csvbuilder import FmuBuilder
+
+
+def test_default_experiment(tmp_path):
+    fmpy = pytest.importorskip(
+        "fmpy", reason="fmpy is not available for testing the produced FMU"
+    )
+
+    script_file = Path(__file__).parent / "slaves/pythonslave_read_file.py"
+    project_file = Path(__file__).parent / "data/hello.txt"
+    fmu = FmuBuilder.build_FMU(script_file, project_files=[project_file], dest=tmp_path, needsExecutionTool="false")
+    assert fmu.exists()
+
+    model_description = fmpy.read_model_description(fmu)