diff --git a/tools/widl/typetree.c b/tools/widl/typetree.c
index 6522e09dacf..9220cfb50e9 100644
--- a/tools/widl/typetree.c
+++ b/tools/widl/typetree.c
@@ -124,7 +124,12 @@ static size_t append_namespaces(char **buf, size_t *len, size_t pos, struct name
     size_t n = 0;
     n += strappend(buf, len, pos + n, "%s", prefix);
     if (nested) n += append_namespace(buf, len, pos + n, namespace, separator, abi_prefix);
-    n += strappend(buf, len, pos + n, "%s", suffix);
+    if (suffix) n += strappend(buf, len, pos + n, "%s", suffix);
+    else if (nested)
+    {
+        n -= strlen(separator);
+        (*buf)[n] = 0;
+    }
     return n;
 }