diff --git a/fec/Makefile b/fec/Makefile
index 21a8e3d..cd71ce6 100644
--- a/fec/Makefile
+++ b/fec/Makefile
@@ -1,7 +1,7 @@
 CC ?= cc
 CFLAGS ?= -O2 -Wall -Wextra -std=c89
 CPPFLAGS ?= -Isrc
-SRC = src/arena.c src/diag.c src/lexer.c src/ast.c src/parser.c src/types.c src/m7.c src/own.c src/check_m7.c src/lower.c src/emit_c_m7.c src/driver.c
+SRC = src/arena.c src/diag.c src/lexer.c src/ast.c src/parser.c src/types.c src/m7.c src/own.c src/check_m7.c src/lower.c src/emitcm7.c src/driver.c
 OBJ = $(SRC:.c=.o)
 
 .PHONY: all clean dos-build
diff --git a/fec/build-dos.bat b/fec/build-dos.bat
index ecde577..104d28f 100644
--- a/fec/build-dos.bat
+++ b/fec/build-dos.bat
@@ -32,7 +32,7 @@ if errorlevel 1 goto build_fail
 wcl -q -za -wx -bt=dos -ml -k32768 -c -fo=lower.obj src\lower.c
 if errorlevel 1 goto build_fail
 rem Use an unambiguous short object name for the M7 emitter source.
-wcl -q -za -wx -bt=dos -ml -k32768 -c -fo=emitc.obj src\emit_c_m7.c
+wcl -q -za -wx -bt=dos -ml -k32768 -c -fo=emitc.obj src\emitcm7.c
 if errorlevel 1 goto build_fail
 wcl -q -za -wx -bt=dos -ml -k32768 -c -fo=driver.obj src\driver.c
 if errorlevel 1 goto build_fail
diff --git a/fec/src/check.c b/fec/src/check.c
index 01a9396..1258857 100644
--- a/fec/src/check.c
+++ b/fec/src/check.c
@@ -811,6 +811,7 @@ static FeType *check_index(FeCheckerState *s, FeNode *n)
 static FeType *check_identifier(FeCheckerState *s, FeNode *n, int read)
 {
     FeSym *sym;
+    (void)read; /* TRIAL PATCH: silence W303 under the check_m7.c wrapper */
     sym = find_symbol(s->scope, n->text ? n->text : "");
     if (!sym) {
         FeType *named=fe_type_intern(&s->c->types,n->text ? n->text : "");
diff --git a/fec/src/check_m7.c b/fec/src/check_m7.c
index 193ecbf..9cfc506 100644
--- a/fec/src/check_m7.c
+++ b/fec/src/check_m7.c
@@ -98,6 +98,7 @@ static FeType *m7_check_expected(FeCheckerState *s, FeNode *value,
     return actual;
 }
 
+/* TRIAL PATCH: m7_error_same was dead (W202); removed for this run.
 static int m7_error_same(FeCheckerState *s, FeType *a, FeType *b)
 {
     FeType *ea;
@@ -108,6 +109,7 @@ static int m7_error_same(FeCheckerState *s, FeType *a, FeType *b)
     eb=fe_m7_error_type(&s->c->types,b);
     return ea && eb && fe_type_equal(ea,eb);
 }
+*/
 
 static FeType *m7_member_field(FeCheckerState *s, FeNode *n, FeType *base)
 {
diff --git a/fec/src/emit_c_m7.c b/fec/src/emitcm7.c
similarity index 100%
rename from fec/src/emit_c_m7.c
rename to fec/src/emitcm7.c
diff --git a/src/ferrolang_vm/registry.py b/src/ferrolang_vm/registry.py
index 74d129a..e967920 100644
--- a/src/ferrolang_vm/registry.py
+++ b/src/ferrolang_vm/registry.py
@@ -17,6 +17,7 @@ M3 = "TESTS\\M3"
 M4 = "TESTS\\M4"
 M5 = "TESTS\\M5"
 M6 = "TESTS\\M6"
+M7 = "TESTS\\M7"
 OUT = "OUT"
 
 # Emitted-C basenames that were hand-shortened for DOS 8.3. Keyed by milestone
@@ -193,6 +194,17 @@ CASES: list[Case] = [
         "okbranch", "okdefer", "okglobcp", "oklast", "okr8free", "okr8join",
         "okr8meth", "okr8stat", "okrebor", "okrtlast", "okshare", "okslreb",
         "okstatic", "oktemp", "oktrim", "okwcall")],
+
+    # -- M7: optionals and error unions ---------------------------------------
+    *[_case(7, name, f"FEC.EXE --check {_fe(M7, name)}", False) for name in (
+        "badcatch", "baddef", "baddir", "badercod", "badernam", "badetype",
+        "badnull", "badoref", "badorel", "badproj", "badqmark", "badret",
+        "badsome", "badtry", "badzero")],
+    *[_case(7, name, _emit(_fe(M7, name), f"{OUT}\\{name.upper()}.C",
+                           output_first=True)) for name in (
+        "okcatch", "okcatmov", "okcvoid", "okdeflt", "okiflet", "okmatch",
+        "oknull", "okorelse", "okpatvw", "okproj", "okrepl", "oktrdef",
+        "oktry")],
 ]
 
 MAX_MILESTONE: int = max(case.milestone for case in CASES)