SF patch #474590 -- RISC OS support
diff --git a/Lib/plat-riscos/riscospath.py b/Lib/plat-riscos/riscospath.py
index c25572b..fb0e477 100644
--- a/Lib/plat-riscos/riscospath.py
+++ b/Lib/plat-riscos/riscospath.py
@@ -103,8 +103,10 @@
     j= a
     for b in p:
         (fs, drive, path)= _split(b)
-        if fs!='' or drive!='' or path[:1] in _roots:
+        if j=='' or fs!='' or drive!='' or path[:1] in _roots:
             j= b
+        elif j[-1]==':':
+            j= j+b
         else:
             j= j+'.'+b
     return j