diff --git a/fact/VERSION b/fact/VERSION
index 9b40aa6..9028ec6 100644
--- a/fact/VERSION
+++ b/fact/VERSION
@@ -1 +1 @@
-0.10.4
+0.10.5
diff --git a/fact/io.py b/fact/io.py
index 3f99159..0b9d3e7 100644
--- a/fact/io.py
+++ b/fact/io.py
@@ -224,7 +224,7 @@ def check_extension(file_path, allowed_extensions=allowed_extensions):
         raise IOError('Allowed formats: {}'.format(allowed_extensions))
 
 
-def to_h5py(filename, df, key='data', mode='w', dtypes=None, index=True, **kwargs):
+def to_h5py(filename, df, key='data', mode='a', dtypes=None, index=True, **kwargs):
     '''
     Write pandas dataframe to h5py style hdf5 file
 
@@ -253,7 +253,7 @@ def to_h5py(filename, df, key='data', mode='w', dtypes=None, index=True, **kwarg
         array = change_recarray_dtype(array, dtypes)
 
     with h5py.File(filename, mode=mode) as f:
-        if mode == 'w':
+        if key not in f:
             initialize_h5py(f, array.dtype, key=key, **kwargs)
 
         append_to_h5py(f, array, key=key)
diff --git a/tests/test_io.py b/tests/test_io.py
index 016bf89..c034d91 100644
--- a/tests/test_io.py
+++ b/tests/test_io.py
@@ -92,6 +92,32 @@ def test_to_h5py_append():
             assert all(df_read[col] == df_written[col])
 
 
+def test_to_h5py_append_second_group():
+    from fact.io import to_h5py, read_h5py
+
+    df1 = pd.DataFrame({
+        'x': np.random.normal(size=50),
+        'N': np.random.randint(0, 10, dtype='uint8')
+    })
+    df2 = pd.DataFrame({
+        'x': np.random.normal(size=50),
+        'N': np.random.randint(0, 10, dtype='uint8')
+    })
+
+    with tempfile.NamedTemporaryFile() as f:
+        to_h5py(f.name, df1, key='g1', index=False)
+        to_h5py(f.name, df2, key='g2', index=False)
+
+        df_g1 = read_h5py(f.name, key='g1')
+        df_g2 = read_h5py(f.name, key='g2')
+
+        for col in df_g1.columns:
+            assert all(df_g1[col] == df1[col])
+
+        for col in df_g2.columns:
+            assert all(df_g2[col] == df2[col])
+
+
 def test_write_data_csv():
     from fact.io import write_data