diff --git a/dlls/msi/database.c b/dlls/msi/database.c
index eaf8ebd..2900860 100644
--- a/dlls/msi/database.c
+++ b/dlls/msi/database.c
@@ -90,6 +90,13 @@ UINT MSI_OpenDatabaseW(LPCWSTR szDBPath, LPCWSTR szPersist, MSIDATABASE **pdb)
     if( !pdb )
         return ERROR_INVALID_PARAMETER;
 
+    if (szPersist - MSIDBOPEN_PATCHFILE >= MSIDBOPEN_READONLY &&
+        szPersist - MSIDBOPEN_PATCHFILE <= MSIDBOPEN_CREATEDIRECT)
+    {
+        TRACE("Database is a patch\n");
+        szPersist -= MSIDBOPEN_PATCHFILE;
+    }
+
     save_path = szDBPath;
     szMode = szPersist;
     if( HIWORD( szPersist ) )
diff --git a/include/msiquery.h b/include/msiquery.h
index 1358033..fa42f17 100644
--- a/include/msiquery.h
+++ b/include/msiquery.h
@@ -75,6 +75,8 @@ typedef enum tagMSIMODIFY
 #define MSIDBOPEN_CREATEDIRECT (LPCWSTR)4
 #endif
 
+#define MSIDBOPEN_PATCHFILE 32 / sizeof(*MSIDBOPEN_READONLY)
+
 typedef enum tagMSIRUNMODE
 {
     MSIRUNMODE_ADMIN = 0,
-- 
1.5.4.3