diff --git a/platform.md b/platform.md
index b26ab00..ca09895 100644
--- a/platform.md
+++ b/platform.md
@@ -71,6 +71,7 @@ Examples of a platform might include:
     - [Environment](#environment)
       - [Buildpack Environment](#buildpack-environment)
         - [Base Image-Provided Variables](#base-image-provided-variables)
+        - [POSIX Path Variables](#posix-path-variables)
         - [User-Provided Variables](#user-provided-variables)
         - [Operator-Defined Variables](#operator-defined-variables)
       - [Launch Environment](#launch-environment)
@@ -1133,6 +1134,8 @@ buildpack without modification:
 |-----------------------------|--------------------------------|
 | `HOME`                      | Current user's home directory  |
 
+##### POSIX Path Variables
+
 The following variables SHOULD be set in the lifecycle execution environment and MAY be modified by prior buildpacks before they are provided to a given buildpack:
 
 | Env Variable      | Layer Path   | Contents         |
@@ -1148,24 +1151,29 @@ The platform SHOULD NOT assume any other base-image-provided environment variabl
 ##### User-Provided Variables
 
 User-provided environment variables MUST be supplied by the platform as files in the `<platform>/env/` directory.
+
 Each file SHALL define a single environment variable, where the file name defines the key and the file contents define the value.
 
-User-provided environment variables MAY be modified by prior buildpacks before they are provided to a given buildpack.
+User-provided environment variables that are [POSIX path variables](#posix-path-variables) MAY be modified by prior buildpacks before they are provided to a given buildpack,
+however the user-provided value is always prepended to the buildpack-provided value.
 
-The platform SHOULD NOT set user-provided environment variables directly in the lifecycle execution environment.
+User-provided environment variables that are not POSIX path variables MAY NOT be modified by prior buildpacks before they are provided to a given buildpack.
 
-The `<platform>/env/` directory follows the same convention as [Environment Variable Modification Rules](https://github.com/buildpacks/spec/blob/main/buildpack.md#environment-variable-modification-rules).
+The platform SHOULD NOT set user-provided environment variables directly in the lifecycle execution environment.
 
 ##### Operator-Defined Variables
-Operator-provided environment varaiables MUST be supplied by the platform as files in the `<build-config>/env/` directory.
+
+Operator-provided environment variables MUST be supplied by the platform as files in the `<build-config>/env/` directory.
 
 Each file SHALL define a single environment variable, where the file name defines the key and the file contents define the value.
 
-Operator-defined environment variables MAY be modified by subsequent buildpacks before they are provided to a given buildpack.
+The `<build-config>/env/` directory follows the [Environment Variable Modification Rules](https://github.com/buildpacks/spec/blob/main/buildpack.md#environment-variable-modification-rules)
+outlined in the [Buildpack Interface Specification](buildpack.md), except for the modification behavior when no period-delimited suffix is provided; when no suffix is provided, the behavior is `default`.
 
-The platform SHOULD NOT set operator-provided environment variables directly in the lifecycle execution environment.
+Operator-defined environment variables MAY be modified by prior buildpacks before they are provided to a given buildpack,
+however the operator-defined value is always applied after the buildpack-provided value.
 
-The `<build-config>/env/` directory follows the [Environment Variable Modification Rules](https://github.com/buildpacks/spec/blob/main/buildpack.md#environment-variable-modification-rules) outlined in the [Buildpack Interface Specification](buildpack.md), except for the modification behavior when no period-delimited suffix is provided; when no suffix is provided, the behavior is `default`.
+The platform SHOULD NOT set operator-provided environment variables directly in the lifecycle execution environment.
 
 #### Launch Environment