diff --git a/Changelog.txt b/Changelog.txt
index 2e35abf..f0c08e6 100644
--- a/Changelog.txt
+++ b/Changelog.txt
@@ -12,7 +12,14 @@ found at:
 === Changes made since last versioned release ===
 
 - [2023.12.01; Maikuolan]: Improved escaping. Added support for specifying a
-  Redis database number to the cache handler.
+  Redis database number to the cache handler (CIDRAM/CIDRAM#540).
+
+- [2023.12.08; Bug-fix; Maikuolan]: Not escaping keys when reconstructing YAML
+  data could prevent successful reprocessing of those keys if said keys
+  contained any hashes or backslashes. The solution is to enforce escaping of
+  keys when such bytes are detected, regardless of how the property for quoting
+  keys is defined. Accordingly, that's been done, and a new method added for
+  that purpose (CIDRAM/CIDRAM#547).
 
 === Version/Release 1.10.0 ===
 MINOR RELEASE.
diff --git a/src/YAML.php b/src/YAML.php
index 22d2e2c..648801b 100644
--- a/src/YAML.php
+++ b/src/YAML.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * YAML handler (last modified: 2023.12.01).
+ * YAML handler (last modified: 2023.12.08).
  *
  * This file is a part of the "common classes package", utilised by a number of
  * packages and projects, including CIDRAM and phpMussel.
@@ -755,7 +755,7 @@ private function processInner(array $Arr, &$Out, $Depth = 0)
                     $Out .= ',';
                 }
                 if (!$Sequential) {
-                    $Out .= ($this->QuoteKeys ? $this->scalarToString($Key) : $Key) . ':';
+                    $Out .= ($this->QuoteKeys ? $this->scalarToString($Key) : $this->escapeKey($Key)) . ':';
                 }
                 if (is_array($Value)) {
                     $this->processInner($Value, $Out, $Depth + 1);
@@ -795,9 +795,9 @@ private function processInner(array $Arr, &$Out, $Depth = 0)
             $ThisDepth = str_repeat($this->Indent, $Depth);
             if ($NullSet && !$Sequential) {
                 $Out .= $ThisDepth . '?';
-                $Value = $Key;
+                $Value = $this->escapeKey($Key);
             } else {
-                $Out .= $ThisDepth . ($Sequential ? '-' : ($this->QuoteKeys ? $this->scalarToString($Key) : $Key) . ':');
+                $Out .= $ThisDepth . ($Sequential ? '-' : ($this->QuoteKeys ? $this->scalarToString($Key) : $this->escapeKey($Key)) . ':');
             }
             if (is_array($Value)) {
                 if ($Depth < $this->FlowRebuildDepth - 1) {
@@ -855,10 +855,10 @@ private function processInner(array $Arr, &$Out, $Depth = 0)
     private function escape($Value = '', $Newlines = true)
     {
         if ($this->Quotes === "'") {
-            return str_replace("'", "''", $Value);
+            return str_replace(['\\', '#', "'"], ['\\\\', '\#', "''"], $Value);
         }
         if ($this->Quotes !== '"') {
-            return $Value;
+            return str_replace(['\\', '#'], ['\\\\', '\#'], $Value);
         }
         $Value = str_replace('\\', '\\\\', $Value);
         if ($Newlines) {
@@ -891,6 +891,23 @@ private function escape($Value = '', $Newlines = true)
         return $Value;
     }
 
+    /**
+     * Escape keys if necessary (or else there could be problems with hashes).
+     *
+     * @param string $Key The key to escape.
+     * @return string The escaped key.
+     */
+    private function escapeKey($Key = '')
+    {
+        if (!is_string($Key)) {
+            return '';
+        }
+        if (strpos($Key, '#') === false && strpos($Key, '\\') === false) {
+            return $Key;
+        }
+        return '"' . str_replace(['\\', '#'], ['\\\\', '\#'], $Key) . '"';
+    }
+
     /**
      * Unescape according to the YAML specification.
      *
@@ -944,9 +961,9 @@ private function unescape($Value = '', $Style = '"')
             return $Value;
         }
         if ($Style === "'" || $Style === "\xe2\x80\x98" || $Style === "\x93") {
-            return str_replace("''", "'", $Value);
+            return str_replace(["''", '\#', '\\\\'], ["'", '#', '\\'], $Value);
         }
-        return $Value;
+        return str_replace(['\#', '\\\\'], ['#', '\\'], $Value);
     }
 
     /**