diff --git a/configure/RULES.Db b/configure/RULES.Db
index f1834c7ec..46d3ad223 100644
--- a/configure/RULES.Db
+++ b/configure/RULES.Db
@@ -13,7 +13,7 @@
 vpath %.dbd $(USR_VPATH) $(SRC_DIRS) $(dir $(DBD))
 vpath %.db $(USR_VPATH) $(SRC_DIRS) $(dir $(DB))
 vpath %.vdb $(USR_VPATH) $(SRC_DIRS) $(dir $(DB))
-vpath %.substitutions $(USR_VPATH) $(SRC_DIRS) $(COMMON_DIR)
+vpath %$(SUBST_SUFFIX) $(USR_VPATH) $(SRC_DIRS) $(COMMON_DIR)
 vpath %.template $(USR_VPATH) $(SRC_DIRS) $(COMMON_DIR)
 vpath bpt%.data $(USR_VPATH) $(SRC_DIRS) $(COMMON_DIR)
 vpath %.acf $(USR_VPATH) $(SRC_DIRS) $(COMMON_DIR)
@@ -45,6 +45,8 @@ DBD += $(foreach type, $(CROSS_TARGET_OS_TYPES), $(DBD_$(type)))
 #
 # ---------------------------------------------------
 
+SUBST_SUFFIX ?= .substitutions
+
 DBDINC_NAME = $(patsubst %.h,%,$(patsubst %.dbd,%,$(DBDINC)))
 DBD += $(addsuffix .dbd,$(DBDINC_NAME))
 INC += $(addsuffix .h,$(DBDINC_NAME))
@@ -66,7 +68,7 @@ SOURCE_DB_bbb = $(foreach dir, $(GENERIC_SRC_DIRS), $(SOURCE_DB_aaa)  )
 SOURCE_DB_aaa = $(addsuffix /$(file), $(dir) )
 
 COMMONS = $(COMMON_DIR)/*.dbd $(COMMON_DIR)/*.db $(COMMON_DIR)/*.h \
-          $(COMMON_DIR)/*.substitutions $(COMMON_DIR)/*.template
+          $(COMMON_DIR)/*$(SUBST_SUFFIX) $(COMMON_DIR)/*.template
 
 # Remove trailing numbers (to 99) on stem
 TEMPLATE1=$(patsubst %0,%,$(patsubst %1,%,$(patsubst %2,%,$(patsubst %3,%,$(patsubst %4,%, \
@@ -230,13 +232,13 @@ menu%.h$(DEP): ../menu%.dbd
 	@$(DBEXPAND) -D $(DBDFLAGS) -o $(COMMONDEP_TARGET) $($*_DBD) > $@
 	@echo "$(COMMONDEP_TARGET): ../Makefile" >> $@
 
-%.db$(RAW)$(DEP): %.substitutions
+%.db$(RAW)$(DEP): %$(SUBST_SUFFIX)
 	@$(RM) $@
 	$(MKMF) -m$@ $(DBFLAGS) $(COMMONDEP_TARGET) $< $(TEMPLATE_FILENAME)
 	@echo "$(COMMONDEP_TARGET): $(TEMPLATE_FILENAME)" >> $@
 	@echo "$@: $(TEMPLATE_FILENAME)" >> $@
 
-%.db$(RAW)$(DEP): ../%.substitutions
+%.db$(RAW)$(DEP): ../%$(SUBST_SUFFIX)
 	@$(RM) $@
 	$(MKMF) -m$@ $(DBFLAGS) $(COMMONDEP_TARGET) $< $(TEMPLATE_FILENAME)
 	@echo "$(COMMONDEP_TARGET): $(TEMPLATE_FILENAME)" >> $@
@@ -270,21 +272,21 @@ $(COMMON_DIR)/%.edf: ../%.sch $(DEPSCHS)
 #  WARNING: CREATESUBSTITUTIONS script needs output dir on command line
 
 ifdef CREATESUBSTITUTIONS
-$(COMMON_DIR)/%.substitutions:
+$(COMMON_DIR)/%$(SUBST_SUFFIX):
 	$(ECHO) "Create substitutions"
 	@$(RM) $@
 	$(CREATESUBSTITUTIONS) $@
 endif
 
-$(INSTALL_DB)/%.substitutions: %.substitutions
+$(INSTALL_DB)/%$(SUBST_SUFFIX): %$(SUBST_SUFFIX)
 	$(ECHO) "Installing db file $@"
 	@$(INSTALL) -d -m $(INSTALL_PERMISSIONS) $< $(@D)
 
-$(INSTALL_DB)/%.substitutions: ../%.substitutions
+$(INSTALL_DB)/%$(SUBST_SUFFIX): ../%$(SUBST_SUFFIX)
 	$(ECHO) "Installing db file $@"
 	@$(INSTALL) -d -m $(INSTALL_PERMISSIONS) $< $(@D)
 
-.PRECIOUS: $(COMMON_DIR)/%.substitutions
+.PRECIOUS: $(COMMON_DIR)/%$(SUBST_SUFFIX)
 
 ##################################################### Template files
 
@@ -396,13 +398,13 @@ $(COMMON_DIR)/%.db$(RAW): $(COMMON_DIR)/%.edf
 	@$(REPLACEVAR) < $*.VAR > $@
 	@$(RM) $*.VAR
 
-$(COMMON_DIR)/%.db$(RAW): %.substitutions
+$(COMMON_DIR)/%.db$(RAW): %$(SUBST_SUFFIX)
 	$(ECHO) "Inflating database from $< $(TEMPLATE_FILENAME)"
 	@$(RM) $@ $*.tmp
 	$(MSI) $(DBFLAGS) -S$< $(TEMPLATE_FILENAME) > $*.tmp
 	$(MV) $*.tmp $@
 
-$(COMMON_DIR)/%.db$(RAW): ../%.substitutions
+$(COMMON_DIR)/%.db$(RAW): ../%$(SUBST_SUFFIX)
 	$(ECHO) "Inflating database from $< $(TEMPLATE_FILENAME)"
 	@$(RM) $@ $*.tmp
 	$(MSI) $(DBFLAGS) -S$< $(TEMPLATE_FILENAME) > $*.tmp