diff --git a/CHANGES.rst b/CHANGES.rst
index eac5f03..eab3765 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -2,6 +2,11 @@
 Changelog
 =========
 
+Version 0.3.15
+==============
+
+- Allow reading of data in append mode.
+
 Version 0.3.14
 ==============
 
diff --git a/pygeobase/io_base.py b/pygeobase/io_base.py
index ff6bf26..91175ca 100644
--- a/pygeobase/io_base.py
+++ b/pygeobase/io_base.py
@@ -442,7 +442,7 @@ def _read_gp(self, gp, **kwargs):
         data : numpy.ndarray
             Data set or None in case of an error.
         """
-        if self.mode in ['w', 'a']:
+        if self.mode in ['w']:
             raise IOError("File is not open in read mode")
 
         data = None
@@ -647,7 +647,7 @@ def _read_gp(self, gp, **kwargs):
         data : object
             pygeobase.object_base.TS object
         """
-        if self.mode in ['w', 'a']:
+        if self.mode in ['w']:
             raise IOError("File is not open in read mode")
 
         data = None
diff --git a/tests/test_io_base.py b/tests/test_io_base.py
index cf18e07..be29695 100644
--- a/tests/test_io_base.py
+++ b/tests/test_io_base.py
@@ -55,10 +55,10 @@ def read_ts(self, gpi, factor=1):
             raise IOError("GPI does not exist")
         return gpi * factor
 
-    def write(self, gpi, data):
+    def write(self, gpi, data, **kwargs):
         return None
 
-    def write_ts(self, gpi, data):
+    def write_ts(self, gpi, data, **kwargs):
         return None
 
     def close(self):
@@ -82,6 +82,18 @@ def test_gridded_ts_base_iter_ts():
         assert gpi == gpi_should.pop(0)
 
 
+def test_gridded_ts_base_read_append():
+    """
+    Test reading in append mode in GriddedTs. Should be allowed.
+    """
+    grid = grids.CellGrid(np.array([1, 2, 3, 4]), np.array([1, 2, 3, 4]),
+                          np.array([4, 4, 2, 1]), gpis=np.array([1, 2, 3, 4]))
+
+    ds = GriddedTsBase("", grid, TestDataset, mode='a')
+    # during iteration the gpis are traversed based on cells for a cell grid
+    assert ds.read(1) == 1
+
+
 def test_gridded_ts_base_iter_gp_IOError_None_yield():
     """
     Test iteration over time series in GriddedTsBase. Should yield None if IOError is raised.