diff --git a/docs/reference/builder.md b/docs/reference/builder.md
index b84f1811f2..c63bcf5347 100644
--- a/docs/reference/builder.md
+++ b/docs/reference/builder.md
@@ -541,6 +541,9 @@ RUN /bin/bash -c 'source $HOME/.bashrc ; echo $HOME'
 > `RUN [ "echo", "$HOME" ]` will not do variable substitution on `$HOME`.
 > If you want shell processing then either use the *shell* form or execute
 > a shell directly, for example: `RUN [ "sh", "-c", "echo $HOME" ]`.
+> When using the exec form and executing a shell directly, as in the case for
+> the shell form, it is the shell that is doing the environment variable
+> expansion, not docker.
 >
 > **Note**:
 > In the *JSON* form, it is necessary to escape backslashes. This is
@@ -607,6 +610,9 @@ instruction as well.
 > `CMD [ "echo", "$HOME" ]` will not do variable substitution on `$HOME`.
 > If you want shell processing then either use the *shell* form or execute
 > a shell directly, for example: `CMD [ "sh", "-c", "echo $HOME" ]`.
+> When using the exec form and executing a shell directly, as in the case for
+> the shell form, it is the shell that is doing the environment variable
+> expansion, not docker.
 
 When used in the shell or exec formats, the `CMD` instruction sets the command
 to be executed when running the image.
@@ -1075,6 +1081,9 @@ sys	0m 0.03s
 > `ENTRYPOINT [ "echo", "$HOME" ]` will not do variable substitution on `$HOME`.
 > If you want shell processing then either use the *shell* form or execute
 > a shell directly, for example: `ENTRYPOINT [ "sh", "-c", "echo $HOME" ]`.
+> When using the exec form and executing a shell directly, as in the case for
+> the shell form, it is the shell that is doing the environment variable
+> expansion, not docker.
 
 ### Shell form ENTRYPOINT example