diff --git a/ph-schematron-pure/src/main/java/com/helger/schematron/pure/binding/xpath/IPSXPathVariables.java b/ph-schematron-pure/src/main/java/com/helger/schematron/pure/binding/xpath/IPSXPathVariables.java
index 1703d6133..5d98ba016 100644
--- a/ph-schematron-pure/src/main/java/com/helger/schematron/pure/binding/xpath/IPSXPathVariables.java
+++ b/ph-schematron-pure/src/main/java/com/helger/schematron/pure/binding/xpath/IPSXPathVariables.java
@@ -23,8 +23,8 @@
 import javax.xml.xpath.XPathExpression;
 
 import com.helger.commons.annotation.ReturnsMutableCopy;
-import com.helger.commons.collection.impl.ICommonsNavigableMap;
-import com.helger.commons.collection.impl.ICommonsSortedSet;
+import com.helger.commons.collection.impl.ICommonsMap;
+import com.helger.commons.collection.impl.ICommonsSet;
 import com.helger.commons.lang.ICloneable;
 
 /**
@@ -39,7 +39,7 @@ public interface IPSXPathVariables extends ICloneable <PSXPathVariables>, Serial
    */
   @Nonnull
   @ReturnsMutableCopy
-  ICommonsNavigableMap <String, XPathExpression> getAll ();
+  ICommonsMap <String, XPathExpression> getAll ();
 
   /**
    * @return All contained variable names. Never <code>null</code>.
@@ -47,7 +47,7 @@ public interface IPSXPathVariables extends ICloneable <PSXPathVariables>, Serial
    */
   @Nonnull
   @ReturnsMutableCopy
-  ICommonsSortedSet <String> getAllNames ();
+  ICommonsSet <String> getAllNames ();
 
   /**
    * @param sName
diff --git a/ph-schematron-pure/src/main/java/com/helger/schematron/pure/binding/xpath/PSXPathVariables.java b/ph-schematron-pure/src/main/java/com/helger/schematron/pure/binding/xpath/PSXPathVariables.java
index fc6c568f1..1e88df731 100644
--- a/ph-schematron-pure/src/main/java/com/helger/schematron/pure/binding/xpath/PSXPathVariables.java
+++ b/ph-schematron-pure/src/main/java/com/helger/schematron/pure/binding/xpath/PSXPathVariables.java
@@ -26,10 +26,9 @@
 import com.helger.commons.ValueEnforcer;
 import com.helger.commons.annotation.Nonempty;
 import com.helger.commons.annotation.ReturnsMutableCopy;
-import com.helger.commons.collection.impl.CommonsTreeMap;
-import com.helger.commons.collection.impl.ICommonsNavigableMap;
-import com.helger.commons.collection.impl.ICommonsSortedSet;
-import com.helger.commons.compare.IComparator;
+import com.helger.commons.collection.impl.CommonsLinkedHashMap;
+import com.helger.commons.collection.impl.ICommonsMap;
+import com.helger.commons.collection.impl.ICommonsSet;
 import com.helger.commons.state.EChange;
 import com.helger.commons.string.StringHelper;
 import com.helger.commons.string.ToStringGenerator;
@@ -44,12 +43,12 @@ public class PSXPathVariables implements IPSXPathVariables
 {
   @Nonnull
   @ReturnsMutableCopy
-  private static ICommonsNavigableMap <String, XPathExpression> _createMap ()
+  private static ICommonsMap <String, XPathExpression> _createMap ()
   {
-    return new CommonsTreeMap <> (IComparator.getComparatorStringLongestFirst ());
+    return new CommonsLinkedHashMap <> ();
   }
 
-  private final ICommonsNavigableMap <String, XPathExpression> m_aMap;
+  private final ICommonsMap <String, XPathExpression> m_aMap;
 
   public PSXPathVariables ()
   {
@@ -138,14 +137,14 @@ public EChange removeAll (@Nullable final Iterable <String> aVars)
 
   @Nonnull
   @ReturnsMutableCopy
-  public ICommonsNavigableMap <String, XPathExpression> getAll ()
+  public ICommonsMap <String, XPathExpression> getAll ()
   {
     return m_aMap.getClone ();
   }
 
   @Nonnull
   @ReturnsMutableCopy
-  public ICommonsSortedSet <String> getAllNames ()
+  public ICommonsSet <String> getAllNames ()
   {
     return m_aMap.copyOfKeySet ();
   }
diff --git a/ph-schematron-pure/src/test/java/com/helger/schematron/pure/supplementary/Issue177Test.java b/ph-schematron-pure/src/test/java/com/helger/schematron/pure/supplementary/Issue177Test.java
new file mode 100644
index 000000000..07da7fe38
--- /dev/null
+++ b/ph-schematron-pure/src/test/java/com/helger/schematron/pure/supplementary/Issue177Test.java
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2014-2024 Philip Helger (www.helger.com)
+ * philip[at]helger[dot]com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.helger.schematron.pure.supplementary;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+import java.io.File;
+
+import javax.annotation.Nonnull;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.helger.commons.io.resource.FileSystemResource;
+import com.helger.schematron.pure.SchematronResourcePure;
+import com.helger.schematron.pure.errorhandler.LoggingPSErrorHandler;
+import com.helger.schematron.svrl.SVRLHelper;
+import com.helger.schematron.svrl.SVRLMarshaller;
+import com.helger.schematron.svrl.jaxb.SchematronOutputType;
+
+public final class Issue177Test
+{
+  private static final Logger LOGGER = LoggerFactory.getLogger (Issue177Test.class);
+
+  public static void validateAndProduceSVRL (@Nonnull final File aSchematron, final File aXML) throws Exception
+  {
+    final SchematronResourcePure aSCH = SchematronResourcePure.fromFile (aSchematron);
+    aSCH.validateCompletely (new LoggingPSErrorHandler ());
+
+    // Perform validation
+    final SchematronOutputType aSVRL = aSCH.applySchematronValidationToSVRL (new FileSystemResource (aXML));
+    assertNotNull (aSVRL);
+    if (true)
+      LOGGER.info (new SVRLMarshaller ().getAsString (aSVRL));
+
+    assertEquals (0, SVRLHelper.getAllFailedAssertionsAndSuccessfulReports (aSVRL).size ());
+  }
+
+  @Test
+  public void testIssue () throws Exception
+  {
+    validateAndProduceSVRL (new File ("src/test/resources/external/issues/github177/schematron.sch"),
+                            new File ("src/test/resources/external/issues/github177/test.xml"));
+  }
+}
diff --git a/ph-schematron-pure/src/test/resources/external/issues/github177/schematron.sch b/ph-schematron-pure/src/test/resources/external/issues/github177/schematron.sch
new file mode 100644
index 000000000..4d5403058
--- /dev/null
+++ b/ph-schematron-pure/src/test/resources/external/issues/github177/schematron.sch
@@ -0,0 +1,10 @@
+<schema xmlns="http://purl.oclc.org/dsdl/schematron" queryBinding="xpath2">
+  <pattern>
+    <let name="var" value="1"/>
+    <let name="var-plus-one" value="$var + 1"/>
+
+    <rule context="/a">
+      <assert role="ERROR" test="$var-plus-one = 2">error message</assert>
+    </rule>
+  </pattern>
+</schema>
diff --git a/ph-schematron-pure/src/test/resources/external/issues/github177/test.xml b/ph-schematron-pure/src/test/resources/external/issues/github177/test.xml
new file mode 100644
index 000000000..859ef5aee
--- /dev/null
+++ b/ph-schematron-pure/src/test/resources/external/issues/github177/test.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<a>
+  <b>
+    <c>1</c>
+  </b>
+  <b>
+    <c>2</c>
+  </b>
+  <b>
+    <c>3</c>
+  </b>
+</a>
\ No newline at end of file