diff --git a/cargo b/cargo
index 5c882eeebf..d081ce15f3 100755
--- a/cargo
+++ b/cargo
@@ -17,6 +17,10 @@ case "$1" in
     toolchain="$rust_nightly"
     shift
     ;;
+  +*)
+    toolchain="${1#+}"
+    shift
+    ;;
   *)
     # shellcheck disable=SC2054 # rust_stable is sourced from rust-version.sh
     toolchain="$rust_stable"