diff --git a/shared/util/codeql/util/UnboundList.qll b/shared/util/codeql/util/UnboundList.qll
index 622895a6bd01..efdcf967ef88 100644
--- a/shared/util/codeql/util/UnboundList.qll
+++ b/shared/util/codeql/util/UnboundList.qll
@@ -10,6 +10,7 @@ overlay[local?]
 module;
 
 private import Location
+private import Strings
 
 /** Provides the input to `Make`. */
 signature module InputSig<LocationSig Location> {
@@ -52,9 +53,35 @@ module Make<LocationSig Location, InputSig<Location> Input> {
   /** Gets the rank of element `e`, which is used internally in the string encoding. */
   int getRank(Element e) { e = DenseRank<DenseRankInput>::denseRank(result) }
 
-  private string encode(Element e) { result = getRank(e).toString() }
+  /** Gets the character that `code` represents when encoding elements. */
+  pragma[nomagic]
+  private string interpretCode(int code) {
+    result = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz".charAt(code)
+  }
+
+  private int codes() { result = strictcount(interpretCode(_)) }
+
+  /**
+   * Gets the `i`th code (modulo `codes()`) in a base-`codes()` integer
+   * representation of `getRank(e)`.
+   */
+  private int getCodePart(Element e, int i) {
+    result = getRank(e) and
+    i = 0
+    or
+    exists(int mid |
+      mid = getCodePart(e, i - 1) and
+      result = mid / codes() and
+      result > 0
+    )
+  }
+
+  pragma[nomagic]
+  private string encode(Element e) {
+    result =
+      strictconcat(string s, int i | s = interpretCode(getCodePart(e, i) % codes()) | s order by i)
+  }
 
-  bindingset[s]
   private Element decode(string s) { encode(result) = s }
 
   /**
@@ -88,7 +115,7 @@ module Make<LocationSig Location, InputSig<Location> Input> {
       // Same as
       // `result = count(this.indexOf("."))`
       // but performs better because it doesn't use an aggregate
-      result = this.regexpReplaceAll("[0-9]+", "").length()
+      result = this.regexpReplaceAll("[a-zA-Z0-9]+", "").length()
     }
 
     /** Gets the list obtained by appending `suffix` onto this list. */
@@ -123,7 +150,7 @@ module Make<LocationSig Location, InputSig<Location> Input> {
         // `regexpCapture` will then always join in both groups, only to afterwards filter
         // based on the requested group (the group number is not part of the binding set
         // of `regexpCapture`)
-        elem = this.regexpCapture("^([0-9]+)\\..*$", 1) and
+        elem = this.regexpCapture("^([a-zA-Z0-9]+)\\..*$", 1) and
         e = decode(elem) and
         suffix = this.suffix(elem.length() + 1)
       )
@@ -133,7 +160,7 @@ module Make<LocationSig Location, InputSig<Location> Input> {
     bindingset[this]
     predicate isSnoc(UnboundList prefix, Element e) {
       // same remark as above about not using multiple capture groups
-      prefix = this.regexpCapture("^(|.+\\.)[0-9]+\\.$", 1) and
+      prefix = this.regexpCapture("^(|.+\\.)[a-zA-Z0-9]+\\.$", 1) and
       e = decode(this.substring(prefix.stringLength(), this.stringLength() - 1))
     }
 
@@ -148,7 +175,7 @@ module Make<LocationSig Location, InputSig<Location> Input> {
      */
     bindingset[this]
     UnboundList getProperPrefix(int i) {
-      exists(string regexp, int occurrenceOffset | regexp = "[0-9]+\\." |
+      exists(string regexp, int occurrenceOffset | regexp = "[a-zA-Z0-9]+\\." |
         exists(this.regexpFind(regexp, i, occurrenceOffset)) and
         result = this.prefix(occurrenceOffset)
       )
@@ -183,6 +210,8 @@ module Make<LocationSig Location, InputSig<Location> Input> {
     UnboundList nil() { result.isEmpty() }
 
     /** Gets the singleton list `e`. */
+    bindingset[e]
+    pragma[inline_late]
     UnboundList singleton(Element e) { result = encode(e) + "." }
 
     /**