diff --git a/src/main/scala/com/datasonnet/DS.scala b/src/main/scala/com/datasonnet/DS.scala
index bd488e93..cefe7743 100644
--- a/src/main/scala/com/datasonnet/DS.scala
+++ b/src/main/scala/com/datasonnet/DS.scala
@@ -2353,10 +2353,11 @@ object DSLowercase extends Library {
         (_, _, value: Val, sep: String) =>
           value match {
             case Val.Str(s) =>
+              val sepLength = sep.length
               Val.Lazy(Val.Str(s.substring(
                 s.indexOf(sep) match {
                   case -1 => s.length
-                  case i => if (sep.equals("")) i else i + 1
+                  case i => if (sep.equals("")) i else i + sepLength
                 }
               ))).force
             case Val.Null => Val.Lazy(Val.Null).force
diff --git a/src/test/java/com/datasonnet/StringsTest.java b/src/test/java/com/datasonnet/StringsTest.java
index 2658439c..a47904f8 100644
--- a/src/test/java/com/datasonnet/StringsTest.java
+++ b/src/test/java/com/datasonnet/StringsTest.java
@@ -485,6 +485,14 @@ void testStrings_substringAfter() {
         value = mapper.transform("{}").replaceAll("\"", "");
         assertEquals("abc", value);
 
+        mapper = new Mapper(lib + pack + ".substringAfter(\"abcba\", \"ab\")", new ArrayList<>(), new HashMap<>(), true);
+        value = mapper.transform("{}").replaceAll("\"", "");
+        assertEquals("cba", value);
+
+        mapper = new Mapper(lib + pack + ".substringAfter(\"abcXXXba\", \"XXX\")", new ArrayList<>(), new HashMap<>(), true);
+        value = mapper.transform("{}").replaceAll("\"", "");
+        assertEquals("ba", value);
+
     }
 
     @Test