diff --git a/Makefile b/Makefile
index fef89c2..91e4296 100644
--- a/Makefile
+++ b/Makefile
@@ -300,7 +300,7 @@
 
 $(OBJ) : $(2)
 	@echo "  CC      $$<"
-	$$(Q)$$(CC) $$(CFLAGS) -c $$< -o $$@
+	$$(Q)$$(CC) $$(CFLAGS) -DIMAGE_BL$(3) -c $$< -o $$@
 
 
 $(PREREQUISITES) : $(2)
@@ -322,7 +322,7 @@
 
 $(OBJ) : $(2)
 	@echo "  AS      $$<"
-	$$(Q)$$(AS) $$(ASFLAGS) -c $$< -o $$@
+	$$(Q)$$(AS) $$(ASFLAGS) -DIMAGE_BL$(3) -c $$< -o $$@
 
 $(PREREQUISITES) : $(2)
 	@echo "  DEPS    $$@"
@@ -359,11 +359,11 @@
 define MAKE_OBJS
 	$(eval C_OBJS := $(filter %.c,$(2)))
 	$(eval REMAIN := $(filter-out %.c,$(2)))
-	$(eval $(foreach obj,$(C_OBJS),$(call MAKE_C,$(1),$(obj))))
+	$(eval $(foreach obj,$(C_OBJS),$(call MAKE_C,$(1),$(obj),$(3))))
 
 	$(eval S_OBJS := $(filter %.S,$(REMAIN)))
 	$(eval REMAIN := $(filter-out %.S,$(REMAIN)))
-	$(eval $(foreach obj,$(S_OBJS),$(call MAKE_S,$(1),$(obj))))
+	$(eval $(foreach obj,$(S_OBJS),$(call MAKE_S,$(1),$(obj),$(3))))
 
 	$(and $(REMAIN),$(error Unexpected source files present: $(REMAIN)))
 endef
@@ -387,7 +387,7 @@
 	$(eval DUMP       := $(BUILD_DIR)/bl$(1).dump)
 	$(eval BIN        := $(BUILD_PLAT)/bl$(1).bin)
 
-	$(eval $(call MAKE_OBJS,$(BUILD_DIR),$(SOURCES)))
+	$(eval $(call MAKE_OBJS,$(BUILD_DIR),$(SOURCES),$(1)))
 	$(eval $(call MAKE_LD,$(LINKERFILE),$(BL$(1)_LINKERFILE)))
 
 $(BUILD_DIR) :
diff --git a/docs/firmware-design.md b/docs/firmware-design.md
index 3203a52..23cae19 100644
--- a/docs/firmware-design.md
+++ b/docs/firmware-design.md
@@ -1226,6 +1226,11 @@
     lib          Yes             Yes             Yes
     services     No              No              Yes
 
+The build system provides a non configurable build option IMAGE_BLx for each
+boot loader stage (where x = BL stage). e.g. for BL1 , IMAGE_BL1 will be
+defined by the build system. This enables the Trusted Firmware to compile
+certain code only for specific boot loader stages
+
 All assembler files have the `.S` extension. The linker source files for each
 boot stage have the extension `.ld.S`. These are processed by GCC to create the
 linker scripts which have the extension `.ld`.