Index: trunk/src/org/openstreetmap/josm/data/osm/NodeGraph.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/osm/NodeGraph.java	(revision 15557)
+++ trunk/src/org/openstreetmap/josm/data/osm/NodeGraph.java	(revision 15558)
@@ -221,4 +221,11 @@
     }
 
+    private List<NodePair> getConnectedPairs (Node node) {
+        List<NodePair> connected = new ArrayList<>();
+        connected.addAll(Optional.ofNullable(successors.get(node)).orElseGet(Collections::emptyList));
+        connected.addAll(Optional.ofNullable(predecessors.get(node)).orElseGet(Collections::emptyList));
+        return connected;
+    }
+
     protected List<NodePair> getOutboundPairs(NodePair pair) {
         return getOutboundPairs(pair.getB());
@@ -340,8 +347,9 @@
             Node n = toVisit.pop();
             if (!visited.contains(n)) {
-                List<NodePair> neighbours = getOutboundPairs(n);
-                for (NodePair pair : neighbours) {
-                    toVisit.addLast(pair.getA());
-                    toVisit.addLast(pair.getB());
+                for (NodePair pair : getConnectedPairs(n)) {
+                    if (n != pair.getA())
+                        toVisit.addLast(pair.getA());
+                    if (n != pair.getB())
+                        toVisit.addLast(pair.getB());
                 }
                 visited.add(n);
Index: trunk/test/data/regress/18387/data.osm
===================================================================
--- trunk/test/data/regress/18387/data.osm	(revision 15558)
+++ trunk/test/data/regress/18387/data.osm	(revision 15558)
@@ -0,0 +1,38 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<osm version='0.6' generator='JOSM'>
+  <node id='-180907' action='modify' visible='true' lat='52.29588639682' lon='13.64411897386' />
+  <node id='-180909' action='modify' visible='true' lat='52.29609561925' lon='13.64572029375' />
+  <node id='61146250' timestamp='2014-11-05T19:19:33Z' uid='115651' user='Rego_Loos' visible='true' version='7' changeset='26578210' lat='52.2948763' lon='13.6442384' />
+  <node id='263019068' timestamp='2014-05-08T09:07:16Z' uid='115651' user='Rego_Loos' visible='true' version='5' changeset='22204763' lat='52.2953129' lon='13.6466991' />
+  <node id='263019078' timestamp='2014-11-05T19:19:34Z' uid='115651' user='Rego_Loos' visible='true' version='6' changeset='26578210' lat='52.2949636' lon='13.6434815' />
+  <node id='263019090' timestamp='2014-05-08T09:07:16Z' uid='115651' user='Rego_Loos' visible='true' version='4' changeset='22204763' lat='52.2952933' lon='13.641262' />
+  <node id='264010827' timestamp='2014-11-05T19:19:34Z' uid='115651' user='Rego_Loos' visible='true' version='5' changeset='26578210' lat='52.2948715' lon='13.6450454' />
+  <node id='264010828' timestamp='2014-11-05T19:19:34Z' uid='115651' user='Rego_Loos' visible='true' version='5' changeset='26578210' lat='52.2949126' lon='13.6453051' />
+  <node id='293894042' timestamp='2014-11-05T19:19:35Z' uid='115651' user='Rego_Loos' visible='true' version='3' changeset='26578210' lat='52.2949155' lon='13.6438623' />
+  <node id='428651766' timestamp='2014-05-08T09:07:18Z' uid='115651' user='Rego_Loos' visible='true' version='2' changeset='22204763' lat='52.2948714' lon='13.6447485' />
+  <node id='2153001668' timestamp='2014-05-08T09:07:17Z' uid='115651' user='Rego_Loos' visible='true' version='2' changeset='22204763' lat='52.295224' lon='13.6416799' />
+  <node id='2153001679' timestamp='2014-11-05T19:19:35Z' uid='115651' user='Rego_Loos' visible='true' version='3' changeset='26578210' lat='52.2949787' lon='13.6455675' />
+  <way id='-180920' action='modify' visible='true'>
+    <nd ref='-180907' />
+    <nd ref='-180909' />
+    <nd ref='263019068' />
+  </way>
+  <way id='24290495' timestamp='2018-05-28T12:52:28Z' uid='2680179' user='SGKW' visible='true' version='11' changeset='59339679'>
+    <nd ref='263019090' />
+    <nd ref='2153001668' />
+    <nd ref='263019078' />
+    <nd ref='293894042' />
+    <nd ref='61146250' />
+    <nd ref='428651766' />
+    <nd ref='264010827' />
+    <nd ref='264010828' />
+    <nd ref='2153001679' />
+    <nd ref='263019068' />
+    <tag k='cycleway' v='opposite' />
+    <tag k='highway' v='residential' />
+    <tag k='maxspeed' v='30' />
+    <tag k='name' v='Kirchsteig' />
+    <tag k='oneway' v='yes' />
+    <tag k='surface' v='asphalt' />
+  </way>
+</osm>
Index: trunk/test/unit/org/openstreetmap/josm/actions/CombineWayActionTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/actions/CombineWayActionTest.java	(revision 15557)
+++ trunk/test/unit/org/openstreetmap/josm/actions/CombineWayActionTest.java	(revision 15558)
@@ -4,7 +4,10 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
@@ -18,4 +21,5 @@
 import org.openstreetmap.josm.data.osm.NodeGraph;
 import org.openstreetmap.josm.data.osm.NodePair;
+import org.openstreetmap.josm.data.osm.Way;
 import org.openstreetmap.josm.io.IllegalDataException;
 import org.openstreetmap.josm.io.OsmReader;
@@ -60,5 +64,5 @@
 
     /**
-     * Non-regression test for bug #1835 (combine way with overlapping ways)
+     * Non-regression test for bug #18385 (combine way with overlapping ways)
      * @throws IOException if any I/O error occurs
      * @throws IllegalDataException if OSM parsing fails
@@ -75,4 +79,23 @@
 
     /**
+     * Non-regression test for bug #18387 (combine new way with oneway)
+     * @throws IOException if any I/O error occurs
+     * @throws IllegalDataException if OSM parsing fails
+     */
+    @Test
+    public void testTicket18387() throws IOException, IllegalDataException {
+        try (InputStream is = TestUtils.getRegressionDataStream(18387, "data.osm")) {
+            DataSet ds = OsmReader.parseDataSet(is, null);
+            ArrayList<Way> selection = new ArrayList<>(ds.getWays());
+            assertEquals(2, selection.size());
+            if (!selection.get(0).isNew())
+                Collections.reverse(selection);
+            NodeGraph graph = NodeGraph.createNearlyUndirectedGraphFromNodeWays(selection);
+            List<Node> path = graph.buildSpanningPathNoRemove();
+            assertTrue(path != null);
+        }
+    }
+
+    /**
      * Unit test of methods {@link NodePair#equals} and {@link NodePair#hashCode}.
      */