diff --git a/python/plugins/processing/algs/qgis/SinglePartsToMultiparts.py b/python/plugins/processing/algs/qgis/SinglePartsToMultiparts.py
index 71421caf154..ac10ad28750 100644
--- a/python/plugins/processing/algs/qgis/SinglePartsToMultiparts.py
+++ b/python/plugins/processing/algs/qgis/SinglePartsToMultiparts.py
@@ -30,7 +30,7 @@ import os
 
 from qgis.PyQt.QtGui import QIcon
 
-from qgis.core import QgsFeature, QgsGeometry, QgsWkbTypes, QgsProcessingUtils, NULL
+from qgis.core import QgsFeature, QgsGeometry, QgsWkbTypes, QgsProcessingUtils
 
 from processing.core.GeoAlgorithm import GeoAlgorithm
 from processing.core.parameters import ParameterVector
@@ -87,13 +87,6 @@ class SinglePartsToMultiparts(GeoAlgorithm):
         for current, feature in enumerate(features):
             atMap = feature.attributes()
             idVar = atMap[index]
-            if idVar in [None, NULL]:
-                outFeat.setAttributes(atMap)
-                outFeat.setGeometry(feature.geometry())
-                writer.addFeature(outFeat)
-                feedback.setProgress(int(current * total))
-                continue
-
             key = str(idVar).strip()
             if key not in collection_geom:
                 collection_geom[key] = []
diff --git a/python/plugins/processing/tests/testdata/custom/single_part_poly.gml b/python/plugins/processing/tests/testdata/custom/single_part_poly.gml
index a10fe7525fe..bf9a0d3462d 100644
--- a/python/plugins/processing/tests/testdata/custom/single_part_poly.gml
+++ b/python/plugins/processing/tests/testdata/custom/single_part_poly.gml
@@ -10,11 +10,11 @@
       <gml:coord><gml:X>8.962880985074626</gml:X><gml:Y>7.163993643533122</gml:Y></gml:coord>
     </gml:Box>
   </gml:boundedBy>
-
+                                                                                              
   <gml:featureMember>
     <ogr:single_part_poly fid="single_part_poly.0">
       <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>0.80194134384858,7.16399364353312 0.672499728706625,4.76932376340694 5.20295625867508,4.2839177066246 5.26276665671642,6.74081294029851 0.80194134384858,7.16399364353312</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
-      <ogr:id></ogr:id>
+      <ogr:id>1</ogr:id>
     </ogr:single_part_poly>
   </gml:featureMember>
   <gml:featureMember>
diff --git a/python/plugins/processing/tests/testdata/expected/single_to_multi.gml b/python/plugins/processing/tests/testdata/expected/single_to_multi.gml
index d86824848d8..de7731f91e6 100644
--- a/python/plugins/processing/tests/testdata/expected/single_to_multi.gml
+++ b/python/plugins/processing/tests/testdata/expected/single_to_multi.gml
@@ -11,11 +11,6 @@
     </gml:Box>
   </gml:boundedBy>
                                                                                                   
-  <gml:featureMember>
-    <ogr:single_to_multi fid="single_part_poly.0">
-      <ogr:geometryProperty><gml:MultiPolygon srsName="EPSG:4326"><gml:polygonMember><gml:Polygon><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>0.80194134384858,7.16399364353312 0.672499728706625,4.76932376340694 5.20295625867508,4.2839177066246 5.26276665671642,6.74081294029851 0.80194134384858,7.16399364353312</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></gml:polygonMember></gml:MultiPolygon></ogr:geometryProperty>
-    </ogr:single_to_multi>
-  </gml:featureMember>
   <gml:featureMember>
     <ogr:single_to_multi fid="single_part_poly.6">
       <ogr:geometryProperty><gml:MultiPolygon srsName="EPSG:4326"><gml:polygonMember><gml:Polygon><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>0.210196746268657,2.19860362686567 0.439859014925373,1.05029228358209 1.15436385074627,1.02477425373134 0.720557343283582,4.0359017761194 0.210196746268657,2.19860362686567</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></gml:polygonMember></gml:MultiPolygon></ogr:geometryProperty>
@@ -23,14 +18,8 @@
     </ogr:single_to_multi>
   </gml:featureMember>
   <gml:featureMember>
-    <ogr:single_to_multi fid="single_part_poly.5">
-      <ogr:geometryProperty><gml:MultiPolygon srsName="EPSG:4326"><gml:polygonMember><gml:Polygon><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>0.592967194029851,-0.17457314925373 1.58817035820896,-2.06290735820895 2.37922928358209,-1.3739205522388 2.63440958208955,0.284751388059703 0.592967194029851,-0.17457314925373</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></gml:polygonMember></gml:MultiPolygon></ogr:geometryProperty>
-      <ogr:id>3</ogr:id>
-    </ogr:single_to_multi>
-  </gml:featureMember>
-  <gml:featureMember>
-    <ogr:single_to_multi fid="single_part_poly.1">
-      <ogr:geometryProperty><gml:MultiPolygon srsName="EPSG:4326"><gml:polygonMember><gml:Polygon><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>6.30900588059701,4.21452798507463 6.00278952238806,2.60689210447761 8.4525203880597,1.81583317910448 8.96288098507463,4.26556404477612 8.24837614925373,7.04702929850746 6.30900588059701,4.21452798507463</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></gml:polygonMember><gml:polygonMember><gml:Polygon><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>3.96134713432836,1.68824302985075 3.93582910447761,-1.14425828358209 8.27389417910448,-1.50151070149254 8.120786,0.64200380597015 3.96134713432836,1.68824302985075</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></gml:polygonMember></gml:MultiPolygon></ogr:geometryProperty>
+    <ogr:single_to_multi fid="single_part_poly.0">
+      <ogr:geometryProperty><gml:MultiPolygon srsName="EPSG:4326"><gml:polygonMember><gml:Polygon><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>0.80194134384858,7.16399364353312 0.672499728706625,4.76932376340694 5.20295625867508,4.2839177066246 5.26276665671642,6.74081294029851 0.80194134384858,7.16399364353312</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></gml:polygonMember><gml:polygonMember><gml:Polygon><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>6.30900588059701,4.21452798507463 6.00278952238806,2.60689210447761 8.4525203880597,1.81583317910448 8.96288098507463,4.26556404477612 8.24837614925373,7.04702929850746 6.30900588059701,4.21452798507463</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></gml:polygonMember><gml:polygonMember><gml:Polygon><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>3.96134713432836,1.68824302985075 3.93582910447761,-1.14425828358209 8.27389417910448,-1.50151070149254 8.120786,0.64200380597015 3.96134713432836,1.68824302985075</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></gml:polygonMember></gml:MultiPolygon></ogr:geometryProperty>
       <ogr:id>1</ogr:id>
     </ogr:single_to_multi>
   </gml:featureMember>
@@ -40,4 +29,10 @@
       <ogr:id>2</ogr:id>
     </ogr:single_to_multi>
   </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_to_multi fid="single_part_poly.5">
+      <ogr:geometryProperty><gml:MultiPolygon srsName="EPSG:4326"><gml:polygonMember><gml:Polygon><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>0.592967194029851,-0.17457314925373 1.58817035820896,-2.06290735820895 2.37922928358209,-1.3739205522388 2.63440958208955,0.284751388059703 0.592967194029851,-0.17457314925373</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></gml:polygonMember></gml:MultiPolygon></ogr:geometryProperty>
+      <ogr:id>3</ogr:id>
+    </ogr:single_to_multi>
+  </gml:featureMember>
 </ogr:FeatureCollection>