diff --git a/README.md b/README.md
index df14c313..be4c50f4 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,13 @@ This is a collection of APIs abstracting platform specific functionality to be l
 
 ## Version History
 
+### Development Build: v1.6.0-rc4+dev21
+
+- Standardize version.h
+- Update Copyright Header
+- See <https://github.com/nasa/PSP/pull/330> and <https://github.com/nasa/cFS/445>
+
+
 ### Development Build: v1.6.0-rc4+dev14
 
 - Remove explicit filename doxygen comments
diff --git a/fsw/mcp750-vxworks/inc/psp_version.h b/fsw/mcp750-vxworks/inc/psp_version.h
index 9764b758..2fa900a9 100644
--- a/fsw/mcp750-vxworks/inc/psp_version.h
+++ b/fsw/mcp750-vxworks/inc/psp_version.h
@@ -27,7 +27,7 @@
 /*
  * Development Build Macro Definitions
  */
-#define CFE_PSP_IMPL_BUILD_NUMBER   14
+#define CFE_PSP_IMPL_BUILD_NUMBER   21
 #define CFE_PSP_IMPL_BUILD_BASELINE "v1.6.0-rc4"
 
 /*
diff --git a/fsw/pc-linux/inc/psp_version.h b/fsw/pc-linux/inc/psp_version.h
index 9764b758..2fa900a9 100644
--- a/fsw/pc-linux/inc/psp_version.h
+++ b/fsw/pc-linux/inc/psp_version.h
@@ -27,7 +27,7 @@
 /*
  * Development Build Macro Definitions
  */
-#define CFE_PSP_IMPL_BUILD_NUMBER   14
+#define CFE_PSP_IMPL_BUILD_NUMBER   21
 #define CFE_PSP_IMPL_BUILD_BASELINE "v1.6.0-rc4"
 
 /*
diff --git a/fsw/pc-rtems/inc/psp_version.h b/fsw/pc-rtems/inc/psp_version.h
index 9764b758..2fa900a9 100644
--- a/fsw/pc-rtems/inc/psp_version.h
+++ b/fsw/pc-rtems/inc/psp_version.h
@@ -27,7 +27,7 @@
 /*
  * Development Build Macro Definitions
  */
-#define CFE_PSP_IMPL_BUILD_NUMBER   14
+#define CFE_PSP_IMPL_BUILD_NUMBER   21
 #define CFE_PSP_IMPL_BUILD_BASELINE "v1.6.0-rc4"
 
 /*