diff --git a/ghc/lib/std/Makefile b/ghc/lib/std/Makefile
index fc3955b0d39dc36c2030dd144362b80b872c745b..75140b8cf3b255488f864a66e0cebb570933e1ea 100644
--- a/ghc/lib/std/Makefile
+++ b/ghc/lib/std/Makefile
@@ -69,6 +69,7 @@ PrelHandle_HC_OPTS       += -H12m
 Time_HC_OPTS             += -H8m
 Complex_HC_OPTS          += -H10m
 IO_HC_OPTS	         += -H12m
+PrelMain_HC_OPTS	 += -fno-prune-tydecls # avoids an apparent bug; ToDo
 
 #-----------------------------------------------------------------------------
 # 	Dependency generation