diff --git a/doc/CHANGES.txt b/doc/CHANGES.txt
index 2f54c375..10a87f59 100644
--- a/doc/CHANGES.txt
+++ b/doc/CHANGES.txt
@@ -6,6 +6,7 @@ ideas/open issues
 iox-ili 1.21.18 (SNAPSHOT)
 -----------------------------
 - Iox2wkb/RingCollector: fix issues with duplicate coordinates (ili2db#510)
+- Iox2wkb/RingCollector: fix issue with inner boundary with arcs continued by outer boundary with straights (ili2db#510)
 
 iox-ili 1.21.17 (2023-02-22)
 -----------------------------
diff --git a/src/main/java/ch/interlis/iox_j/wkb/LineSegment.java b/src/main/java/ch/interlis/iox_j/wkb/LineSegment.java
index d2e27d8b..841dad51 100644
--- a/src/main/java/ch/interlis/iox_j/wkb/LineSegment.java
+++ b/src/main/java/ch/interlis/iox_j/wkb/LineSegment.java
@@ -66,7 +66,10 @@ public int size(){
     public LineSegment splitTailAt(Coordinate coordinate){
         int pos = coordinatesMap.get(coordinate);
         if (pos == coordinates.size() - 1) return null;
-
+        if(pos!=0 && pos%2==0 && wkbType==WKBConstants.wkbCircularString) {
+            throw new IllegalArgumentException("A mid-point of an ARC can not start a ring "+coordinate.toString());
+        }
+        
         List<Coordinate> tail = coordinates.subList(pos, coordinates.size());
         LineSegment result = new LineSegment(wkbType);
 
diff --git a/src/main/java/ch/interlis/iox_j/wkb/RingCollector.java b/src/main/java/ch/interlis/iox_j/wkb/RingCollector.java
index 4f0aea57..f0137c86 100644
--- a/src/main/java/ch/interlis/iox_j/wkb/RingCollector.java
+++ b/src/main/java/ch/interlis/iox_j/wkb/RingCollector.java
@@ -86,7 +86,15 @@ else if (repairSelfTouchingRing && getSegmentIdx(getCurrentRing(),coordinate)!=n
         }
 
         segment = getCurrentSegment();
-        segment.add(coordinate);
+        // different/new segment required?
+        if (!segment.trySetWkbType(WkbType)) {
+            Coordinate lastCoord = segment.getLast();
+            segment = new LineSegment(WkbType);
+            segment.add(lastCoord);
+            ring.add(segment);
+        }else {
+            segment.add(coordinate);
+        }
     }
 
     private void extractInnerRing(Coordinate coordinate) {
@@ -106,7 +114,6 @@ private void extractInnerRing(Coordinate coordinate) {
         }
 
         extractedRing.get(extractedRing.size() - 1).add(coordinate);
-
         rings.add(extractedRing);
     }
 
diff --git a/src/main/java/ch/interlis/iox_j/wkb/Wkb2iox.java b/src/main/java/ch/interlis/iox_j/wkb/Wkb2iox.java
index 5c29dc60..fb79991c 100644
--- a/src/main/java/ch/interlis/iox_j/wkb/Wkb2iox.java
+++ b/src/main/java/ch/interlis/iox_j/wkb/Wkb2iox.java
@@ -324,7 +324,7 @@ private IomObject readCompoundCurve() throws IOException
 	    			}else{
 		    			IomObject arcPt=readPoint();coordi++;
 		    			if(coordi>=coordc){
-		    				throw new IllegalStateException("missing coord");
+		    				throw new IllegalStateException("missing coord (arcPt "+arcPt.toString()+")");
 		    			}
 		    			IomObject endPt=readPoint();
 		    			endPt.setobjecttag(Iom_jObject.ARC);
diff --git a/src/test/java/ch/interlis/iox_j/wkb/Iox2wkbTest.java b/src/test/java/ch/interlis/iox_j/wkb/Iox2wkbTest.java
index 854498b3..15542ddb 100644
--- a/src/test/java/ch/interlis/iox_j/wkb/Iox2wkbTest.java
+++ b/src/test/java/ch/interlis/iox_j/wkb/Iox2wkbTest.java
@@ -473,9 +473,9 @@ public void surfaceReapirTouchingRingMultipleInnerRingSegments() throws Exceptio
         // verify
 
         Wkb2iox test=new Wkb2iox();
-        assertEquals("MULTISURFACE {surface SURFACE {boundary [BOUNDARY {polyline POLYLINE {sequence SEGMENTS {segment [COORD {C1 2645116.0, C2 1247903.0}, COORD {C1 2650896.0, C2 1245677.0}, COORD {C1 2650921.0, C2 1247915.0}, COORD {C1 2650921.0, C2 1247915.0}, COORD {C1 2650921.0, C2 1250572.0}, COORD {C1 2645116.0, C2 1247903.0}]}}}, BOUNDARY {polyline POLYLINE {sequence SEGMENTS {segment [COORD {C1 2650921.0, C2 1247915.0}, ARC {A1 2649853.0, A2 1247123.0, C1 2648651.0, C2 1247238.0}, COORD {C1 2648618.0, C2 1248913.0}, ARC {A1 2649677.0, A2 1248889.0, C1 2650921.0, C2 1247915.0}]}}}]}}",test.read(wkb).toString());
+        assertEquals("MULTISURFACE {surface SURFACE {boundary [BOUNDARY {polyline POLYLINE {sequence SEGMENTS {segment [COORD {C1 2645116.0, C2 1247903.0}, COORD {C1 2650896.0, C2 1245677.0}, COORD {C1 2650921.0, C2 1247915.0}, COORD {C1 2650921.0, C2 1250572.0}, COORD {C1 2645116.0, C2 1247903.0}]}}}, BOUNDARY {polyline POLYLINE {sequence SEGMENTS {segment [COORD {C1 2650921.0, C2 1247915.0}, ARC {A1 2649853.0, A2 1247123.0, C1 2648651.0, C2 1247238.0}, COORD {C1 2648618.0, C2 1248913.0}, ARC {A1 2649677.0, A2 1248889.0, C1 2650921.0, C2 1247915.0}]}}}]}}",test.read(wkb).toString());
         String wkbText=Iox2wkb.bytesToHex(wkb);
-        assertEquals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wkbText);
+        assertEquals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wkbText);
     }
     
     @Test