diff --git a/docs/manual/customize-outside-br.adoc b/docs/manual/customize-outside-br.adoc
index 78065489d4..8a76f3a998 100644
--- a/docs/manual/customize-outside-br.adoc
+++ b/docs/manual/customize-outside-br.adoc
@@ -58,10 +58,11 @@ We can switch to another br2-external tree at any time:
 buildroot/ $ make BR2_EXTERNAL=/where/we/have/bar xconfig
 ----
 
-We can also use multiple br2-external trees:
+We can also use multiple br2-external trees, by specifying a space-separated
+list of paths to use:
 
 ----
-buildroot/ $ make BR2_EXTERNAL=/path/to/foo:/where/we/have/bar menuconfig
+buildroot/ $ make BR2_EXTERNAL="/path/to/foo /where/we/have/bar" menuconfig
 ----
 
 Or disable the usage of any br2-external tree:
diff --git a/support/scripts/br2-external b/support/scripts/br2-external
index 474feaded7..641f8e18ae 100755
--- a/support/scripts/br2-external
+++ b/support/scripts/br2-external
@@ -34,6 +34,9 @@ main() {
         error "Cannot create output directory '%s'\n" "${outputdir}"
     fi
 
+    # Historically, BR2_EXTERNAL could also be colon-separated, so for
+    # backward compatibility, keep splitting on colons (in addition to
+    # spaces).
     # shellcheck disable=SC2068  # We do want to split on spaces
     do_validate "${outputdir}" ${@//:/ }
     do_mk "${outputdir}"