diff --git a/dlls/urlmon/tests/uri.c b/dlls/urlmon/tests/uri.c
index 3e6f5a89208..04534413bda 100644
--- a/dlls/urlmon/tests/uri.c
+++ b/dlls/urlmon/tests/uri.c
@@ -4209,6 +4209,62 @@ static const uri_properties uri_tests[] = {
             {URL_SCHEME_ABOUT,S_OK,FALSE},
             {URLZONE_INVALID,E_NOTIMPL,FALSE}
         }
+    },
+    {   "mk:@MSITStore:C:\\Program Files/AutoCAD 2008\\Help/acad_acg.chm::/WSfacf1429558a55de1a7524c1004e616f8b-322b.htm",0,S_OK,FALSE,
+        Uri_HAS_ABSOLUTE_URI|Uri_HAS_DISPLAY_URI|Uri_HAS_EXTENSION|Uri_HAS_PATH|Uri_HAS_PATH_AND_QUERY|
+        Uri_HAS_RAW_URI|Uri_HAS_SCHEME_NAME|Uri_HAS_HOST_TYPE|Uri_HAS_SCHEME,
+        FALSE,
+        {
+            {"mk:@MSITStore:C:\\Program%20Files/AutoCAD%202008\\Help/acad_acg.chm::/WSfacf1429558a55de1a7524c1004e616f8b-322b.htm",S_OK,FALSE},
+            {"",S_FALSE,FALSE},
+            {"mk:@MSITStore:C:\\Program%20Files/AutoCAD%202008\\Help/acad_acg.chm::/WSfacf1429558a55de1a7524c1004e616f8b-322b.htm",S_OK,FALSE},
+            {"",S_FALSE,FALSE},
+            {".htm",S_OK,FALSE},
+            {"",S_FALSE,FALSE},
+            {"",S_FALSE,FALSE},
+            {"",S_FALSE,FALSE},
+            {"@MSITStore:C:\\Program%20Files/AutoCAD%202008\\Help/acad_acg.chm::/WSfacf1429558a55de1a7524c1004e616f8b-322b.htm",S_OK,FALSE},
+            {"@MSITStore:C:\\Program%20Files/AutoCAD%202008\\Help/acad_acg.chm::/WSfacf1429558a55de1a7524c1004e616f8b-322b.htm",S_OK,FALSE},
+            {"",S_FALSE,FALSE},
+            {"mk:@MSITStore:C:\\Program Files/AutoCAD 2008\\Help/acad_acg.chm::/WSfacf1429558a55de1a7524c1004e616f8b-322b.htm",S_OK,FALSE},
+            {"mk",S_OK,FALSE},
+            {"",S_FALSE,FALSE},
+            {"",S_FALSE,FALSE}
+        },
+        {
+            {Uri_HOST_UNKNOWN,S_OK,FALSE},
+            {0,S_FALSE,FALSE},
+            {URL_SCHEME_MK,S_OK,FALSE},
+            {URLZONE_INVALID,E_NOTIMPL,FALSE}
+        }
+    },
+    {   "mk:@MSITStore:Z:\\home\\test\\chm\\silqhelp.chm::/thesilqquickstartguide.htm",0,S_OK,FALSE,
+        Uri_HAS_ABSOLUTE_URI|Uri_HAS_DISPLAY_URI|Uri_HAS_EXTENSION|Uri_HAS_PATH|Uri_HAS_PATH_AND_QUERY|
+        Uri_HAS_RAW_URI|Uri_HAS_SCHEME_NAME|Uri_HAS_HOST_TYPE|Uri_HAS_SCHEME,
+        FALSE,
+        {
+            {"mk:@MSITStore:Z:\\home\\test\\chm\\silqhelp.chm::/thesilqquickstartguide.htm",S_OK,FALSE},
+            {"",S_FALSE,FALSE},
+            {"mk:@MSITStore:Z:\\home\\test\\chm\\silqhelp.chm::/thesilqquickstartguide.htm",S_OK,FALSE},
+            {"",S_FALSE,FALSE},
+            {".htm",S_OK,FALSE},
+            {"",S_FALSE,FALSE},
+            {"",S_FALSE,FALSE},
+            {"",S_FALSE,FALSE},
+            {"@MSITStore:Z:\\home\\test\\chm\\silqhelp.chm::/thesilqquickstartguide.htm",S_OK,FALSE},
+            {"@MSITStore:Z:\\home\\test\\chm\\silqhelp.chm::/thesilqquickstartguide.htm",S_OK,FALSE},
+            {"",S_FALSE,FALSE},
+            {"mk:@MSITStore:Z:\\home\\test\\chm\\silqhelp.chm::/thesilqquickstartguide.htm",S_OK,FALSE},
+            {"mk",S_OK,FALSE},
+            {"",S_FALSE,FALSE},
+            {"",S_FALSE,FALSE}
+        },
+        {
+            {Uri_HOST_UNKNOWN,S_OK,FALSE},
+            {0,S_FALSE,FALSE},
+            {URL_SCHEME_MK,S_OK,FALSE},
+            {URLZONE_INVALID,E_NOTIMPL,FALSE}
+        }
     }
 };
 
diff --git a/dlls/urlmon/uri.c b/dlls/urlmon/uri.c
index ef66186f0ab..2aee38a46ba 100644
--- a/dlls/urlmon/uri.c
+++ b/dlls/urlmon/uri.c
@@ -3081,6 +3081,11 @@ static BOOL canonicalize_path_opaque(const parse_data *data, Uri *uri, DWORD fla
                 if(!computeOnly)
                     uri->canon_uri[uri->canon_len] = *ptr;
                 ++uri->canon_len;
+            } else if(data->scheme_type == URL_SCHEME_MK && *ptr == '\\') {
+                /* MK URIs don't get '\\' percent encoded. */
+                if(!computeOnly)
+                    uri->canon_uri[uri->canon_len] = *ptr;
+                ++uri->canon_len;
             } else {
                 if(!computeOnly)
                     pct_encode_val(*ptr, uri->canon_uri+uri->canon_len);