diff --git a/docs/src/main/asciidoc/building-native-image.adoc b/docs/src/main/asciidoc/building-native-image.adoc
index beb1707172bfe..73ccb5df7fb49 100644
--- a/docs/src/main/asciidoc/building-native-image.adoc
+++ b/docs/src/main/asciidoc/building-native-image.adoc
@@ -102,6 +102,7 @@ export PATH=${GRAALVM_HOME}/bin:$PATH
 ====
 GraalVM binaries are not (yet) notarized for macOS Catalina as reported in this https://github.com/oracle/graal/issues/1724[GraalVM issue]. This means that you may see the following error when using `gu`:
 
+[source,shell]
 ----
 “gu” cannot be opened because the developer cannot be verified
 ----