diff --git a/core/Makefile b/core/Makefile
index de5b7bf..db70d2f 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -300,7 +300,7 @@
 $(INSTALLED_BOOTIMAGE_TARGET): $(MKBOOTIMG) $(INTERNAL_BOOTIMAGE_FILES)
 	$(call pretty,"Target boot image: $@")
 	$(hide) $(MKBOOTIMG) $(INTERNAL_BOOTIMAGE_ARGS) --output $@
-	$(hide) $(call assert-max-image-size,$@,$(BOARD_BOOTIMAGE_PARTITION_SIZE))
+	$(hide) $(call assert-max-image-size,$@,$(BOARD_BOOTIMAGE_PARTITION_SIZE),raw)
 endif # TARGET_BOOTIMAGE_USE_EXT2
 
 else	# TARGET_NO_KERNEL
@@ -578,7 +578,7 @@
 	$(MKBOOTFS) $(TARGET_RECOVERY_ROOT_OUT) | $(MINIGZIP) > $(recovery_ramdisk)
 	$(MKBOOTIMG) $(INTERNAL_RECOVERYIMAGE_ARGS) --output $@
 	@echo ----- Made recovery image -------- $@
-	$(hide) $(call assert-max-image-size,$@,$(BOARD_RECOVERYIMAGE_PARTITION_SIZE))
+	$(hide) $(call assert-max-image-size,$@,$(BOARD_RECOVERYIMAGE_PARTITION_SIZE),raw)
 
 else
 INSTALLED_RECOVERYIMAGE_TARGET :=
@@ -663,7 +663,7 @@
 $(INSTALLED_SYSTEMIMAGE): $(BUILT_SYSTEMIMAGE) $(RECOVERY_FROM_BOOT_PATCH) | $(ACP)
 	@echo "Install system fs image: $@"
 	$(copy-file-to-target)
-	$(hide) $(call assert-max-image-size,$@ $(RECOVERY_FROM_BOOT_PATCH),$(BOARD_SYSTEMIMAGE_PARTITION_SIZE))
+	$(hide) $(call assert-max-image-size,$@ $(RECOVERY_FROM_BOOT_PATCH),$(BOARD_SYSTEMIMAGE_PARTITION_SIZE),yaffs)
 
 systemimage: $(INSTALLED_SYSTEMIMAGE)
 
@@ -672,7 +672,7 @@
 	            | $(INTERNAL_MKUSERFS)
 	@echo "make $@: ignoring dependencies"
 	$(call build-systemimage-target,$(INSTALLED_SYSTEMIMAGE))
-	$(hide) $(call assert-max-image-size,$(INSTALLED_SYSTEMIMAGE),$(BOARD_SYSTEMIMAGE_PARTITION_SIZE))
+	$(hide) $(call assert-max-image-size,$(INSTALLED_SYSTEMIMAGE),$(BOARD_SYSTEMIMAGE_PARTITION_SIZE),yaffs)
 
 #######
 ## system tarball
@@ -709,7 +709,7 @@
     $(call pretty,"Target userdata fs image: $(INSTALLED_USERDATAIMAGE_TARGET)")
     @mkdir -p $(TARGET_OUT_DATA)
     $(call build-userimage-ext2-target,$(TARGET_OUT_DATA),$(INSTALLED_USERDATAIMAGE_TARGET),userdata,)
-    $(hide) $(call assert-max-image-size,$(INSTALLED_USERDATAIMAGE_TARGET),$(BOARD_USERDATAIMAGE_PARTITION_SIZE))
+    $(hide) $(call assert-max-image-size,$(INSTALLED_USERDATAIMAGE_TARGET),$(BOARD_USERDATAIMAGE_PARTITION_SIZE),yaffs)
 endef
 
 else # TARGET_USERIMAGES_USE_EXT2 != true
@@ -719,7 +719,7 @@
     $(call pretty,"Target userdata fs image: $(INSTALLED_USERDATAIMAGE_TARGET)")
     @mkdir -p $(TARGET_OUT_DATA)
     $(hide) $(MKYAFFS2) -f $(TARGET_OUT_DATA) $(INSTALLED_USERDATAIMAGE_TARGET)
-    $(hide) $(call assert-max-image-size,$(INSTALLED_USERDATAIMAGE_TARGET),$(BOARD_USERDATAIMAGE_PARTITION_SIZE))
+    $(hide) $(call assert-max-image-size,$(INSTALLED_USERDATAIMAGE_TARGET),$(BOARD_USERDATAIMAGE_PARTITION_SIZE),yaffs)
 endef
 endif # TARGET_USERIMAGES_USE_EXT2
 
diff --git a/core/definitions.mk b/core/definitions.mk
index 883afda..49356a1 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -1574,6 +1574,7 @@
 
 # $(1): The file(s) to check (often $@)
 # $(2): The maximum total image size, in decimal bytes
+# $(3): the type of filesystem "yaffs" or "raw"
 #
 # If $(2) is empty, evaluates to "true"
 #
@@ -1587,9 +1588,15 @@
   printname=$$(echo -n "$(1)" | tr " " +); \
   echo "$$printname total size is $$total"; \
   img_blocksize=$(call image-size-from-data-size,$(BOARD_FLASH_BLOCK_SIZE)); \
+  if [ "$(3)" == "yaffs" ]; then \
+    reservedblocks=5; \
+  else \
+    reselvedblocks=0; \
+  fi; \
   twoblocks=$$((img_blocksize * 2)); \
   onepct=$$((((($(2) / 100) - 1) / img_blocksize + 1) * img_blocksize)); \
-  reserve=$$((twoblocks > onepct ? twoblocks : onepct)); \
+  reserve=$$(((twoblocks > onepct ? twoblocks : onepct) + \
+               reservedblocks * img_blocksize)); \
   maxsize=$$(($(2) - reserve)); \
   if [ "$$total" -gt "$$maxsize" ]; then \
     echo "error: $$printname too large ($$total > [$(2) - $$reserve])"; \