diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/metapath/function/library/FnSubstring.java b/core/src/main/java/gov/nist/secauto/metaschema/core/metapath/function/library/FnSubstring.java
index ef01b92db..f88e5df22 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/metapath/function/library/FnSubstring.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/metapath/function/library/FnSubstring.java
@@ -95,7 +95,7 @@ private static ISequence<IStringItem> execute(
     IStringItem sourceString = FunctionUtils.asType(ObjectUtils.requireNonNull(arguments.get(0).getFirstItem(true)));
     IIntegerItem start = FunctionUtils.asType(ObjectUtils.requireNonNull(arguments.get(1).getFirstItem(true)));
     IIntegerItem length = FunctionUtils.asType(ObjectUtils.requireNonNull(arguments.get(2).getFirstItem(true)));
-    return ISequence.of(su1bstring(sourceString, start, length));
+    return ISequence.of(substring(sourceString, start, length));
   }
 
   /**