diff --git a/oscar/main.cpp b/oscar/main.cpp
index f0db9a7d..d56fc8e4 100644
--- a/oscar/main.cpp
+++ b/oscar/main.cpp
@@ -307,7 +307,9 @@ int main(int argc, char *argv[]) {
             QString datadir ;
             if ((i+1) < args.size()) {
                 datadir = args[++i];
-                settings.setValue("Settings/AppData", homeDocs+datadir);
+                if (datadir.length() < 2 || datadir.at(1) != ":")  // Allow a Windows driver letter (but not UNC)
+                    datadir = homeDocs+datadir;
+                settings.setValue("Settings/AppData", datadir);
 //            force_data_dir = true;
             } else {
                 fprintf(stderr, "Missing argument to --datadir\n");