diff --git a/ixmp4/data/db/optimization/equation/model.py b/ixmp4/data/db/optimization/equation/model.py
index e7588043..ee8d2898 100644
--- a/ixmp4/data/db/optimization/equation/model.py
+++ b/ixmp4/data/db/optimization/equation/model.py
@@ -31,11 +31,12 @@ def validate_data(self, key: Any, data: dict[str, Any]) -> dict[str, Any]:
         data_to_validate = copy.deepcopy(data)
         del data_to_validate["levels"]
         del data_to_validate["marginals"]
-        _ = utils.validate_data(
-            host=self,
-            data=data_to_validate,
-            columns=self.columns,
-        )
+        if data_to_validate != {}:
+            _ = utils.validate_data(
+                host=self,
+                data=data_to_validate,
+                columns=self.columns,
+            )
         return data
 
     __table_args__ = (db.UniqueConstraint("name", "run__id"),)
diff --git a/ixmp4/data/db/optimization/variable/model.py b/ixmp4/data/db/optimization/variable/model.py
index 32cfae59..548e7499 100644
--- a/ixmp4/data/db/optimization/variable/model.py
+++ b/ixmp4/data/db/optimization/variable/model.py
@@ -32,11 +32,12 @@ def validate_data(self, key: Any, data: dict[str, Any]) -> dict[str, Any]:
         data_to_validate = copy.deepcopy(data)
         del data_to_validate["levels"]
         del data_to_validate["marginals"]
-        _ = utils.validate_data(
-            host=self,
-            data=data_to_validate,
-            columns=self.columns,
-        )
+        if data_to_validate != {}:
+            _ = utils.validate_data(
+                host=self,
+                data=data_to_validate,
+                columns=self.columns,
+            )
         return data
 
     __table_args__ = (db.UniqueConstraint("name", "run__id"),)