diff --git a/src/qtgui/rclmain_w.cpp b/src/qtgui/rclmain_w.cpp
index a99f953a..9ca258dc 100644
--- a/src/qtgui/rclmain_w.cpp
+++ b/src/qtgui/rclmain_w.cpp
@@ -1232,7 +1232,12 @@ void RclMain::startPreview(int docnum, Rcl::Doc doc, int mod)
 	doc.getmeta(Rcl::Doc::keyudi, &udi);
 	if (!udi.empty()) {
 	    string sig;
-	    FileInterner::makesig(theconfig, doc, sig);
+	    if (!FileInterner::makesig(theconfig, doc, sig)) {
+		QMessageBox::warning(0, "Recoll", 
+				     tr("Can't access file: ") + 
+				     QString::fromLocal8Bit(doc.url.c_str()));
+		return;
+	    }
 	    if (rcldb->needUpdate(udi, sig)) {
 		QString msg = 
 		    tr("Index not up to date for this file. "
diff --git a/src/rcldb/rcldb.cpp b/src/rcldb/rcldb.cpp
index e333161c..a18eb409 100644
--- a/src/rcldb/rcldb.cpp
+++ b/src/rcldb/rcldb.cpp
@@ -314,13 +314,15 @@ bool Db::Native::dbDataToRclDoc(Xapian::docid docid, std::string &data,
     if (!parms.ok())
 	return false;
 
+    // Set xdocid at once so that we can call whatDbIdx()
+    doc.xdocid = docid;
     // Compute what index this comes from, and check for path translations
     string dbdir = m_rcldb->m_basedir;
     if (!m_rcldb->m_extraDbs.empty()) {
-	// As per trac.xapian.org/wiki/FAQ/MultiDatabaseDocumentID
-	unsigned int idxi = (docid-1) % (m_rcldb->m_extraDbs.size()+1);
-	// idxi is in [0, extraDbs.size()]. 0 is the base index, 1-n index
-	// into the additional dbs array
+	unsigned int idxi = m_rcldb->whatDbIdx(doc);
+
+	// idxi is in [0, extraDbs.size()]. 0 is for the main index,
+	// idxi-1 indexes into the additional dbs array.
 	if (idxi) {
 	    dbdir = m_rcldb->m_extraDbs[idxi - 1];
 	}
@@ -349,7 +351,6 @@ bool Db::Native::dbDataToRclDoc(Xapian::docid docid, std::string &data,
     parms.get(Doc::keyfs, doc.fbytes);
     parms.get(Doc::keyds, doc.dbytes);
     parms.get(Doc::keysig, doc.sig);
-    doc.xdocid = docid;
 
     // Normal key/value pairs:
     vector<string> keys = parms.getNames(string());
@@ -847,13 +848,13 @@ bool Db::rmQueryDb(const string &dir)
 // http://trac.xapian.org/wiki/FAQ/MultiDatabaseDocumentID
 size_t Db::whatDbIdx(const Doc& doc)
 {
-    LOGDEB(("Db::whatDbIdx: xdocid %lu, %u extraDbs\n", 
-	    (unsigned long)doc.xdocid, m_extraDbs.size()));
+    LOGDEB1(("Db::whatDbIdx: xdocid %lu, %u extraDbs\n", 
+	     (unsigned long)doc.xdocid, m_extraDbs.size()));
     if (doc.xdocid == 0) 
 	return (size_t)-1;
     if (m_extraDbs.size() == 0)
 	return 0;
-    return doc.xdocid % (m_extraDbs.size()+1);
+    return (doc.xdocid - 1) % (m_extraDbs.size() + 1);
 }
 
 bool Db::testDbDir(const string &dir, bool *stripped_p)