diff --git a/radicale/app/propfind.py b/radicale/app/propfind.py
index 68145e23..3d674c96 100644
--- a/radicale/app/propfind.py
+++ b/radicale/app/propfind.py
@@ -129,7 +129,8 @@ def xml_propfind_response(
 
     if share:
         # backmap
-        uri = uri.replace(share['PathMapped'], share['PathOrToken'])
+        if uri.startswith(share['PathMapped']):
+            uri = share['PathOrToken'] + uri.removeprefix(share['PathMapped'])
         if share_bday_automap and not uri.endswith("/"):
             uri = uri.rstrip(".vcf") + ".ics"
 
@@ -217,7 +218,8 @@ def xml_propfind_response(
             child_element.text = xmlutils.make_href(base_prefix, path)
             if share:
                 # backmap
-                child_element.text = child_element.text.replace(share['PathMapped'], share['PathOrToken'])
+                if child_element.text.startswith(share['PathMapped']):
+                    child_element.text = share['PathOrToken'] + child_element.text.removeprefix(share['PathMapped'])
                 if share_bday_automap:
                     child_element.text = child_element.text.rstrip(".vcf") + ".ics"
             element.append(child_element)
@@ -256,13 +258,15 @@ def xml_propfind_response(
         elif tag == xmlutils.make_clark("D:current-user-principal"):
             if user:
                 child_element = ET.Element(xmlutils.make_clark("D:href"))
-                child_element.text = xmlutils.make_href(
-                    base_prefix, "/%s/" % user)
                 if share:
                     # backmap
-                    child_element.text = child_element.text.replace(share['Owner'], share['User'])
+                    child_element.text = xmlutils.make_href(
+                        base_prefix, "/%s/" % share['User'])
                     if share_bday_automap:
                         child_element.text = child_element.text.rstrip(".vcf") + ".ics"
+                else:
+                    child_element.text = xmlutils.make_href(
+                        base_prefix, "/%s/" % user)
                 element.append(child_element)
             else:
                 element.append(ET.Element(
diff --git a/radicale/app/report.py b/radicale/app/report.py
index cd51a41f..1c853cdb 100644
--- a/radicale/app/report.py
+++ b/radicale/app/report.py
@@ -749,9 +749,12 @@ def xml_item_response(base_prefix: str, href: str,
         logger.debug("TRACE/REPORT/xml_report: href=%r", href_element.text)
     if share:
         # backmap
-        href_element.text = href_element.text.replace(share['PathMapped'], share['PathOrToken'])
+        if href_element.text.startswith(share['PathMapped']):
+            href_element.text = share['PathOrToken'] + href_element.text.removeprefix(share['PathMapped'])
         if share_bday_automap:
             href_element.text = href_element.text.rstrip(".vcf") + ".ics"
+        if logger.isEnabledFor(logging.DEBUG):
+            logger.debug("TRACE/REPORT/xml_report: href=%r (backmapped)", href_element.text)
     response.append(href_element)
 
     if found_item:
@@ -790,12 +793,17 @@ def retrieve_items(
            gets set to ``True``."""
         nonlocal collection_requested
         for hreference in hreferences:
+            if logger.isEnabledFor(logging.DEBUG):
+                logger.debug("TRACE/REPORT/xml_report: hreference=%r", hreference)
             if share:
                 # map back to owner
-                hreference = hreference.replace(share['PathOrToken'], share['PathMapped'])
+                if hreference.startswith(share['PathOrToken']):
+                    hreference = share['PathMapped'] + hreference.removeprefix(share['PathOrToken'])
                 if share['Conversion'] == "bday":
                     if not hreference.endswith('/'):
                         hreference = hreference.rstrip(".ics") + ".vcf"
+                if logger.isEnabledFor(logging.DEBUG):
+                    logger.debug("TRACE/REPORT/xml_report: hreference=%r (backmapped)", hreference)
             try:
                 name = pathutils.name_from_path(hreference, collection)
             except ValueError as e: