diff --git a/core/Makefile b/core/Makefile
index 3f08f0e..fa0550c 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -126,6 +126,7 @@
 			BUILD_NUMBER="$(BUILD_NUMBER)" \
 			PLATFORM_VERSION="$(PLATFORM_VERSION)" \
 			PLATFORM_SDK_VERSION="$(PLATFORM_SDK_VERSION)" \
+			PLATFORM_VERSION_CODENAME="$(PLATFORM_VERSION_CODENAME)" \
 			BUILD_VERSION_TAGS="$(BUILD_VERSION_TAGS)" \
 			TARGET_BOOTLOADER_BOARD_NAME="$(TARGET_BOOTLOADER_BOARD_NAME)" \
 			BUILD_FINGERPRINT="$(BUILD_FINGERPRINT)" \
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 578d779..902afed 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -39,17 +39,27 @@
   # which is the version that we reveal to the end user.
   # Update this value when the platform version changes (rather
   # than overriding it somewhere else).  Can be an arbitrary string.
-  PLATFORM_VERSION := 1.5
+  PLATFORM_VERSION := Donut
 endif
 
 ifeq "" "$(PLATFORM_SDK_VERSION)"
   # This is the canonical definition of the SDK version, which defines
-  # the set of APIs and functionality available in the platform.  This is
-  # a single integer, that increases monotonically as updates to the SDK
-  # are released.
+  # the set of APIs and functionality available in the platform.  It
+  # is a single integer that increases monotonically as updates to
+  # the SDK are released.  It should only be incremented when the APIs for
+  # the new release are frozen (so that developers don't write apps against
+  # intermediate builds).  During development, this number remains at the
+  # SDK version the branch is based on and PLATFORM_VERSION_CODENAME holds
+  # the code-name of the new development work.
   PLATFORM_SDK_VERSION := 3
 endif
 
+ifeq "" "$(PLATFORM_VERSION_CODENAME)"
+  # This is the current development code-name, if the build is not a final
+  # release build.  If this is a final release build, it is simply "REL".
+  PLATFORM_VERSION_CODENAME := Donut
+endif
+
 ifeq "" "$(BUILD_ID)"
   # Used to signify special builds.  E.g., branches and/or releases,
   # like "M5-RC7".  Can be an arbitrary string, but must be a single