diff --git a/src/ast/ast.h b/src/ast/ast.h
index 944c089f3..93f456965 100644
--- a/src/ast/ast.h
+++ b/src/ast/ast.h
@@ -1379,7 +1379,7 @@ enum proof_gen_mode {
 // -----------------------------------
 
 class ast_manager {
-    friend basic_decl_plugin;
+    friend class basic_decl_plugin;
 protected:
     struct config {
         typedef ast_manager              value_manager;