diff --git a/meson.build b/meson.build
index 04ec9a9e8d..303dba1af8 100644
--- a/meson.build
+++ b/meson.build
@@ -59,8 +59,10 @@ if not meson.is_subproject() and cc.get_id() == 'msvc'
   endif
 endif
 
-# Ensure that MSVC interprets all source code as UTF-8
-if cc.get_id() == 'msvc'
+# Ensure that MSVC interprets all source code as UTF-8. Only do this when we're
+# not a subproject, because subprojects are not allowed to call
+# add_global_arguments().
+if not meson.is_subproject() and cc.get_id() == 'msvc'
   add_global_arguments(
       cc.get_supported_arguments(['/utf-8']), # set the input encoding to utf-8
       language: ['c', 'cpp'])