-GHC_STAGE1 = $(GHC_COMPILER_DIR)/stage1/ghc-inplace
-GHC_STAGE2 = $(GHC_COMPILER_DIR)/stage2/ghc-inplace
-GHC_STAGE3 = $(GHC_COMPILER_DIR)/stage3/ghc-inplace
+GHC_STAGE1 = $(GHC_COMPILER_DIR)/stage1/ghc-inplace -no-user-package-conf
+GHC_STAGE2 = $(GHC_COMPILER_DIR)/stage2/ghc-inplace -no-user-package-conf
+GHC_STAGE3 = $(GHC_COMPILER_DIR)/stage3/ghc-inplace -no-user-package-conf
+
+# NOTE: add -no-user-package-conf for stage 1-3 above, so that
+# we avoid picking up any packages the user might happen to have
+# installed for this GHC version. They are bound to be incompatible
+# with the packages we built in the tree.