diff --git a/pyaerocom/colocation/colocation_setup.py b/pyaerocom/colocation/colocation_setup.py
index 3203679e0..c30e83276 100644
--- a/pyaerocom/colocation/colocation_setup.py
+++ b/pyaerocom/colocation/colocation_setup.py
@@ -464,12 +464,16 @@ def validate_no_forbidden_keys(self):
             if key in self.model_fields:
                 raise ValidationError
 
-    @cached_property
-    def basedir_logfiles(self):
-        p = Path(self.basedir_coldata) / "logfiles"
-        if not p.exists():
-            p.mkdir(parents=True, exist_ok=True)
-        return str(p)
+        return self
+
+    @model_validator(mode="after")
+    # @classmethod
+    def validate_start_stop_xand(self):
+        if not (self.start and self.stop):
+            if self.start or self.stop:
+                raise ValueError("Both start and stop need to be provided or both not provided.")
+
+    #     return self
 
     @model_validator(mode="after")
     @classmethod
@@ -492,6 +496,13 @@ def validate_obs_config(cls, v: PyaroConfig):
                 cls.obs_id = v.name
         return v
 
+    @cached_property
+    def basedir_logfiles(self):
+        p = Path(self.basedir_coldata) / "logfiles"
+        if not p.exists():
+            p.mkdir(parents=True, exist_ok=True)
+        return str(p)
+
     def add_glob_meta(self, **kwargs):
         """
         Add global metadata to :attr:`add_meta`
diff --git a/pyaerocom/colocation/colocator.py b/pyaerocom/colocation/colocator.py
index c3e5283fd..ce6ea960d 100644
--- a/pyaerocom/colocation/colocator.py
+++ b/pyaerocom/colocation/colocator.py
@@ -914,8 +914,13 @@ def _infer_start_stop_yr_from_model_reader(self):
         self.stop = last
 
     def _check_set_start_stop(self):
-        if self.colocation_setup.start is None:
+        if self.colocation_setup.start is None and self.colocation_setup.stop is None:
             self._infer_start_stop_yr_from_model_reader()
+            self.start, self.stop = start_stop(self.start, self.stop)
+        else:
+            self.start, self.stop = start_stop(
+                self.colocation_setup.start, self.colocation_setup.stop
+            )
         if self.colocation_setup.model_use_climatology:
             if self.colocation_setup.stop is not None or not isinstance(
                 self.colocation_setup.start, int
@@ -925,7 +930,6 @@ def _check_set_start_stop(self):
                     'climatology fields, please specify "start" as integer '
                     'denoting the year, and set "stop"=None'
                 )
-        self.start, self.stop = start_stop(self.colocation_setup.start, self.colocation_setup.stop)
 
     def _coldata_savename(self, obs_var, mod_var, ts_type, **kwargs):
         """Get filename of colocated data file for saving"""
diff --git a/tests/colocation/test_colocator.py b/tests/colocation/test_colocator.py
index 1431ffd7d..17c8450c5 100644
--- a/tests/colocation/test_colocator.py
+++ b/tests/colocation/test_colocator.py
@@ -69,6 +69,7 @@ def setup():
         obs_id="AeronetSunV3L2Subset.daily",
         obs_vars="od550aer",
         start=2010,
+        stop=2011,
         raise_exceptions=True,
         reanalyse_existing=True,
     )
@@ -180,6 +181,7 @@ def test_Colocator__coldata_savename(setup):
     setup["model_name"] = "model"
     setup["filter_name"] = ALL_REGION_NAME
     setup["start"] = 2015
+    setup["stop"] = 2016
     col_stp = ColocationSetup(**setup)
     col = Colocator(col_stp)
     col._check_set_start_stop()