diff --git a/make-includes/build_document_rules.make b/make-includes/build_document_rules.make
index 4bb19f6..45cef18 100755
--- a/make-includes/build_document_rules.make
+++ b/make-includes/build_document_rules.make
@@ -366,20 +366,27 @@
 # (assuming that this variable points to a directory on the network) the
 # appropriate share has been mounted.
 #
+# This checks each file in the build directory against the corresponding
+# file in the install directory. The local file is only copied to the
+# install directory if it is newer, or the remote file doesn't exist. I
+# was going to do the "newer" testing using a target rule that dealt with
+# each file individually, but for some weird reason it would ignore any
+# additional files appended to the *_INSTALL_FILES variables. So I've done
+# it with a foreach instead, which _does_ work. (Ick, although ironically
+# the code is shorter.)
+#
 # !!! How do we get it to also install any extra files that we require
 # for a particular content file (e.g., the SQL code for Tutorial 3)? !!!
 #
-install-questions: $(QUESTION_INSTALL_FILES)
+install-questions:
 	@test -d $(HANDBOOK_INSTALL_ROOT)
-ifneq ($(strip $(QUESTION_INSTALL_FILES)),)
-	cp $(QUESTION_INSTALL_FILES) $(INSTALL_DIRECTORY)
-endif
+	@mkdir -p $(INSTALL_DIRECTORY)
+	@$(foreach f,$(QUESTION_INSTALL_FILES),if test ! -f $(INSTALL_DIRECTORY)/$(f) -o $(f) -nt $(INSTALL_DIRECTORY)/$(f); then echo "Installing $(f)"; cp $(f) $(INSTALL_DIRECTORY); fi;)
 
-install-answers: $(ANSWER_INSTALL_FILES)
+install-answers:
 	@test -d $(HANDBOOK_INSTALL_ROOT)
-ifneq ($(strip $(ANSWER_INSTALL_FILES)),)
-	cp $(ANSWER_INSTALL_FILES) $(INSTALL_DIRECTORY)
-endif
+	@mkdir -p $(INSTALL_DIRECTORY)
+	@$(foreach f,$(ANSWER_INSTALL_FILES),if test ! -f $(INSTALL_DIRECTORY)/$(f) -o $(f) -nt $(INSTALL_DIRECTORY)/$(f); then echo "Installing $(f)"; cp $(f) $(INSTALL_DIRECTORY); fi;)
 
 
 ################################################################################
@@ -436,6 +443,7 @@
 	@echo "DERIVED_WEB_FILES = [$(DERIVED_WEB_FILES)]"
 	@echo "DERIVED_PRINT_FILES = [$(DERIVED_PRINT_FILES)]"
 	@echo "CONTENT_SRC = [$(CONTENT_SRC)]"
+	@echo "INSTALL_DIRECTORY = [$(INSTALL_DIRECTORY)]"
 	@echo "QUESTION_INSTALL_FILES = [$(QUESTION_INSTALL_FILES)]"
 	@echo "ANSWER_INSTALL_FILES = [$(ANSWER_INSTALL_FILES)]"
 	@echo "WEB_CLEAN_FILES = [$(WEB_CLEAN_FILES)]"