diff --git a/Makefile b/Makefile
index 529b904..feca34c 100644
--- a/Makefile
+++ b/Makefile
@@ -903,14 +903,24 @@
 
 export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH)
 
-# FIXME: The asm symlink changes when $(ARCH) changes. That's
-# hard to detect, but I suppose "make mrproper" is a good idea
-# before switching between archs anyway.
+# The asm symlink changes when $(ARCH) changes.
+# Detect this and ask user to run make mrproper
 
-include/asm:
-	@echo '  SYMLINK $@ -> include/asm-$(SRCARCH)'
-	$(Q)if [ ! -d include ]; then mkdir -p include; fi;
-	@ln -fsn asm-$(SRCARCH) $@
+include/asm: FORCE
+	$(Q)set -e; asmlink=`readlink include/asm | cut -d '-' -f 2`;   \
+	if [ -L include/asm ]; then                                     \
+		if [ "$$asmlink" != "$(SRCARCH)" ]; then                \
+			echo "ERROR: the symlink $@ points to asm-$$asmlink but asm-$(SRCARCH) was expected"; \
+			echo "       set ARCH or save .config and run 'make mrproper' to fix it";             \
+			exit 1;                                         \
+		fi;                                                     \
+	else                                                            \
+		echo '  SYMLINK $@ -> include/asm-$(SRCARCH)';          \
+		if [ ! -d include ]; then                               \
+			mkdir -p include;                               \
+		fi;                                                     \
+		ln -fsn asm-$(SRCARCH) $@;                              \
+	fi
 
 # Generate some files
 # ---------------------------------------------------------------------------