diff --git a/bin/tagpreview.sh b/bin/tagpreview.sh
index 0bc0b01..e22a732 100755
--- a/bin/tagpreview.sh
+++ b/bin/tagpreview.sh
@@ -30,6 +30,12 @@ else
   exit 1
 fi
 
+# Ex mode starts on the last line, so an entry with no address would report the
+# end of the file as the tag. Every other path refuses such an entry
+if [ -z "${EXCMD}" ]; then
+  exit 1
+fi
+
 # The address comes from a tags file, which can be untrusted, and a preview runs
 # as soon as an entry is highlighted. Sandboxed as a builtin tag jump is, so that
 # it cannot run a shell command or touch a file. ':sandbox' on its own only covers