diff --git a/tests/syntax/ast_diff_1.i b/tests/syntax/ast_diff_1.i
index 623a7b7ba8797268ddb4ed2c52561bba933a2979..7afc3a0e3b37b57df5eb2bfe9d78d281e6e14d44 100644
--- a/tests/syntax/ast_diff_1.i
+++ b/tests/syntax/ast_diff_1.i
@@ -1,6 +1,7 @@
 /* run.config
    MODULE: @PTEST_NAME@
-     OPT: -then -ast-diff %{dep:ast_diff_2.i}
+     OPT: -then -ast-diff %{dep:ast_diff_2.c}
+     OPT: -then -ast-diff %{dep:ast_diff_2.c} -cpp-extra-args="-DADD_ENUM_TAG"
 */
 int X;
 int Y=3;
diff --git a/tests/syntax/ast_diff_2.i b/tests/syntax/ast_diff_2.c
similarity index 96%
rename from tests/syntax/ast_diff_2.i
rename to tests/syntax/ast_diff_2.c
index b83f852c99db2529cb9c88adc25f950c8b39b5d8..c0bd72914c114fde906e283bda7ba599497e621a 100644
--- a/tests/syntax/ast_diff_2.i
+++ b/tests/syntax/ast_diff_2.c
@@ -90,7 +90,10 @@ void with_goto_unchanged(int c) {
 
 enum e {
   t = 1,
-  u = t + 2
+  u = t + 2,
+#ifdef ADD_ENUM_TAG
+  v = t + u,
+#endif
 };
 
 struct s { char c[t]; };
diff --git a/tests/syntax/oracle/ast_diff_1.res.oracle b/tests/syntax/oracle/ast_diff_1.0.res.oracle
similarity index 97%
rename from tests/syntax/oracle/ast_diff_1.res.oracle
rename to tests/syntax/oracle/ast_diff_1.0.res.oracle
index 05acd5419b7b6707fdc2d1af47d639babf898d64..040eb7eac6a64962c2abd84ec40b54ea065123b1 100644
--- a/tests/syntax/oracle/ast_diff_1.res.oracle
+++ b/tests/syntax/oracle/ast_diff_1.0.res.oracle
@@ -1,5 +1,5 @@
 [kernel] Parsing ast_diff_1.i (no preprocessing)
-[kernel] Parsing ast_diff_2.i (no preprocessing)
+[kernel] Parsing ast_diff_2.c (with preprocessing)
 [AST diff test] Showing correspondances between orig_default and default
 [AST diff test] Variable i:  => i
 [AST diff test] Variable local_var_use:  => local_var_use
diff --git a/tests/syntax/oracle/ast_diff_1.1.res.oracle b/tests/syntax/oracle/ast_diff_1.1.res.oracle
new file mode 100644
index 0000000000000000000000000000000000000000..1fe85b83738a956efe119cd4c29b473fbeea6ede
--- /dev/null
+++ b/tests/syntax/oracle/ast_diff_1.1.res.oracle
@@ -0,0 +1,43 @@
+[kernel] Parsing ast_diff_1.i (no preprocessing)
+[kernel] Parsing ast_diff_2.c (with preprocessing)
+[kernel] Parsing ast_diff_1.i (no preprocessing)
+[AST diff test] Showing correspondances between orig_default and default
+[AST diff test] Variable use_logic_builtin:  => use_logic_builtin
+[AST diff test] Variable x:  => x
+[AST diff test] Variable y:  => y
+[AST diff test] Variable has_static_local:  => has_static_local
+[AST diff test] Variable decl:  => decl
+[AST diff test] Variable used_in_decl:  => used_in_decl
+[AST diff test] Variable ptr_func:  => ptr_func
+[AST diff test] Variable i:  => i
+[AST diff test] Variable local_var_use:  => local_var_use
+[AST diff test] Variable v:  => w
+[AST diff test] Variable a:  => q
+[AST diff test] Variable x:  => z
+[AST diff test] Variable y:  => t
+[AST diff test] Variable s: N/A
+[AST diff test] Variable use_s: N/A
+[AST diff test] Variable with_goto_changed:  => with_goto_changed
+[AST diff test] Variable X:  => X
+[AST diff test] Variable Y: N/A
+[AST diff test] Variable c:  => c
+[AST diff test] Variable f:  => f
+[AST diff test] Variable with_goto_unchanged:  => with_goto_unchanged
+[AST diff test] Variable x:  => x
+[AST diff test] Variable c:  => c
+[AST diff test] Variable g:  => g
+[AST diff test] Variable se:  => se
+[AST diff test] Variable has_static_local_x:  => has_static_local_y
+[AST diff test] Variable h:  => h
+[AST diff test] Function use_logic_builtin:  => use_logic_builtin
+[AST diff test] Function has_static_local:  => has_static_local
+[AST diff test] Function decl:  => decl
+[AST diff test] Function i:  => i
+[AST diff test] Function local_var_use:  => local_var_use
+[AST diff test] Function use_s: N/A
+[AST diff test] Function with_goto_changed: -> with_goto_changed (body changed)
+[AST diff test] Function f:  => f
+[AST diff test] Function with_goto_unchanged:  => with_goto_unchanged
+[AST diff test] Function g: N/A
+[AST diff test] Function se: -> se (body changed)
+[AST diff test] Function h: -> h (body changed)