diff --git a/tracetools_analysis/tracetools_analysis/data_model/__init__.py b/tracetools_analysis/tracetools_analysis/data_model/__init__.py
index c2744aa..3364fad 100644
--- a/tracetools_analysis/tracetools_analysis/data_model/__init__.py
+++ b/tracetools_analysis/tracetools_analysis/data_model/__init__.py
@@ -22,4 +22,6 @@ class DataModel():
     Contains data for an analysis to use. This is a middleground between trace events data and the
     output data of an analysis. It uses pandas `DataFrame` directly.
     """
-    pass
+
+    def __init__(self) -> None:
+        pass
diff --git a/tracetools_analysis/tracetools_analysis/data_model/cpu_time.py b/tracetools_analysis/tracetools_analysis/data_model/cpu_time.py
index 21d003d..07dece0 100644
--- a/tracetools_analysis/tracetools_analysis/data_model/cpu_time.py
+++ b/tracetools_analysis/tracetools_analysis/data_model/cpu_time.py
@@ -28,6 +28,7 @@ class CpuTimeDataModel(DataModel):
 
     def __init__(self) -> None:
         """Constructor."""
+        super().__init__()
         self.times = pd.DataFrame(columns=[
             'tid',
             'start_timestamp',
diff --git a/tracetools_analysis/tracetools_analysis/data_model/profile.py b/tracetools_analysis/tracetools_analysis/data_model/profile.py
index 00deb64..035c6e0 100644
--- a/tracetools_analysis/tracetools_analysis/data_model/profile.py
+++ b/tracetools_analysis/tracetools_analysis/data_model/profile.py
@@ -24,6 +24,7 @@ class ProfileDataModel(DataModel):
 
     def __init__(self) -> None:
         """Constructor."""
+        super().__init__()
         self.times = pd.DataFrame(columns=[
             'tid',
             'depth',
diff --git a/tracetools_analysis/tracetools_analysis/data_model/ros.py b/tracetools_analysis/tracetools_analysis/data_model/ros.py
index 056d0a8..e1064db 100644
--- a/tracetools_analysis/tracetools_analysis/data_model/ros.py
+++ b/tracetools_analysis/tracetools_analysis/data_model/ros.py
@@ -27,6 +27,8 @@ class RosDataModel(DataModel):
     """
 
     def __init__(self) -> None:
+        """Constructor."""
+        super().__init__()
         # Objects (one-time events, usually when something is created)
         self.contexts = pd.DataFrame(columns=['context_handle',
                                               'timestamp',