diff --git a/antigen.zsh b/antigen.zsh
index ce6b68e..1c0e0cc 100644
--- a/antigen.zsh
+++ b/antigen.zsh
@@ -418,7 +418,17 @@ antigen () {
     done
 
     local keyword_args="$(
-            echo "$positional_args" | tr , '\n' | sed -r 's/(\??)$/:\1/'
+            # Positional arguments can double up as keyword arguments too.
+            echo "$positional_args" | tr , '\n' |
+                while read line; do
+                    if [[ $line == *\? ]]; then
+                        echo "${line%?}:?"
+                    else
+                        echo "$line:"
+                    fi
+                done
+
+            # Specified keyword arguments.
             echo "$spec" | cut -d\; -f2 | tr , '\n'
             )"
     local keyword_args_count="$(echo $keyword_args | awk -F, '{print NF}')"