diff --git a/src/xmltree.c b/src/xmltree.c
index 273355379..5ce90c0f4 100644
--- a/src/xmltree.c
+++ b/src/xmltree.c
@@ -24,6 +24,7 @@
 #include <libxml/valid.h>
 #include <libxml/xpath.h>
 #include <libxml/xpathInternals.h>
+#include <libxml/xmlversion.h>
 
 #include <xmlsec/xmlsec.h>
 #include <xmlsec/xmltree.h>
@@ -705,7 +706,11 @@ int
 xmlSecReplaceNodeBufferAndReturn(xmlNodePtr node, const xmlSecByte *buffer, xmlSecSize size, xmlNodePtr *replaced) {
     xmlNodePtr results = NULL;
     xmlNodePtr next = NULL;
+#if (LIBXML_VERSION >= 21500)
+    xmlChar *oldenc;
+#else  /* (LIBXML_VERSION >= 21500) */
     const xmlChar *oldenc;
+#endif /* (LIBXML_VERSION >= 21500) */
     int len;
     xmlParserErrors ret;