diff --git a/python/plugins/processing/algs/gdal/Buffer.py b/python/plugins/processing/algs/gdal/Buffer.py
index d3f23497bf44..ab1a3b115142 100644
--- a/python/plugins/processing/algs/gdal/Buffer.py
+++ b/python/plugins/processing/algs/gdal/Buffer.py
@@ -100,9 +100,12 @@ def getConsoleCommands(self, parameters, context, feedback, executing=True):
         if source is None:
             raise QgsProcessingException(self.invalidSourceError(parameters, self.INPUT))
         fields = source.fields()
-        source_details = self.getOgrCompatibleSource(self.INPUT, parameters, context, feedback, executing)
-
-        geometry = self.parameterAsString(parameters, self.GEOMETRY, context)
+        source_details = self.getOgrCompatibleSource(self.INPUT, parameters, context, feedback, executing=True)
+        # QgsVectorFileWriter defaults to geometry column called geom when exporting virtual, memory and grass layer
+        if source_details.layer_name == 'INPUT' and 'INPUT.gpkg' in source_details.connection_string:
+            geometry = parameters[self.GEOMETRY] = 'geom'
+        else:
+            geometry = self.parameterAsString(parameters, self.GEOMETRY, context)
         distance = self.parameterAsDouble(parameters, self.DISTANCE, context)
         fieldName = self.parameterAsString(parameters, self.FIELD, context)
         dissolve = self.parameterAsBoolean(parameters, self.DISSOLVE, context)
@@ -122,6 +125,7 @@ def getConsoleCommands(self, parameters, context, feedback, executing=True):
         arguments = [
             output_details.connection_string,
             source_details.connection_string,
+            '-nlt PROMOTE_TO_MULTI',
             '-dialect',
             'sqlite',
             '-sql'
diff --git a/python/plugins/processing/algs/gdal/GdalAlgorithm.py b/python/plugins/processing/algs/gdal/GdalAlgorithm.py
index d896673a45ca..d4bdc52c8529 100644
--- a/python/plugins/processing/algs/gdal/GdalAlgorithm.py
+++ b/python/plugins/processing/algs/gdal/GdalAlgorithm.py
@@ -84,7 +84,7 @@ def getOgrCompatibleSource(self,
             parameters = {parameter_name: parameters[parameter_name].source}
 
         input_layer = self.parameterAsVectorLayer(parameters, parameter_name, context)
-        if input_layer is None or input_layer.providerType() in ('memory', 'grass'):
+        if input_layer is None or input_layer.providerType() in ('virtual', 'memory', 'grass'):
             if executing:
                 # parameter is not a vector layer - try to convert to a source compatible with OGR
                 # and extract selection if required