diff --git a/README.adoc b/README.adoc
index aadb3b4..ed3fab1 100644
--- a/README.adoc
+++ b/README.adoc
@@ -53,7 +53,7 @@ NOTE: All of the example outputs above were last generated/updated on May 3rd 20
 
 == Usage
 Stop doing this:
-[source, docker]
+[source, dockerfile]
 ----
 FROM ubuntu-debootstrap:14.04
 RUN apt-get update -q \
@@ -64,7 +64,7 @@ ENTRYPOINT ["mysql"]
 ----
 This took 28 seconds to build and yields a 169 MB image.
 Start doing this:
-[source, docker]
+[source, dockerfile]
 ----
 FROM alpine:3.9
 RUN apk add --no-cache mysql-client
diff --git a/docs/usage.adoc b/docs/usage.adoc
index fc71079..7b34471 100644
--- a/docs/usage.adoc
+++ b/docs/usage.adoc
@@ -10,7 +10,7 @@ The `--no-cache` argument prevents `apk` from caching the package index - someth
 
 === Example
 This is an example of a complete Dockerfile for `nginx`:
-[source, docker]
+[source, dockerfile]
 ----
 FROM alpine
 
@@ -24,7 +24,7 @@ CMD ["nginx", "-g", "daemon off;"]
 Another great `apk` feature is the concept of user-defined virtual packages.
 Packages added under a virtual package name can later be removed as one group.
 An example use-case would be removing all build dependencies at once, as in this example:
-[source, docker]
+[source, dockerfile]
 ----
 FROM alpine