diff --git a/test/blackbox-tests/test-cases/merlin/dune b/test/blackbox-tests/test-cases/merlin/dune
new file mode 100644
index 00000000000..b11bdc2d42d
--- /dev/null
+++ b/test/blackbox-tests/test-cases/merlin/dune
@@ -0,0 +1,3 @@
+(cram
+ (applies_to :whole_subtree)
+ (alias all-merlin-tests))
diff --git a/test/blackbox-tests/test-cases/merlin/suffix.t/alterexe.aml b/test/blackbox-tests/test-cases/merlin/suffix.t/alterexe.aml
new file mode 100644
index 00000000000..7fa6dfdfda4
--- /dev/null
+++ b/test/blackbox-tests/test-cases/merlin/suffix.t/alterexe.aml
@@ -0,0 +1 @@
+print_endline "Not so alternative"
diff --git a/test/blackbox-tests/test-cases/merlin/suffix.t/dune b/test/blackbox-tests/test-cases/merlin/suffix.t/dune
new file mode 100644
index 00000000000..2910d5bd975
--- /dev/null
+++ b/test/blackbox-tests/test-cases/merlin/suffix.t/dune
@@ -0,0 +1,2 @@
+(executable
+ (name alterexe))
diff --git a/test/blackbox-tests/test-cases/merlin/suffix.t/dune-project b/test/blackbox-tests/test-cases/merlin/suffix.t/dune-project
new file mode 100644
index 00000000000..fa76dd55498
--- /dev/null
+++ b/test/blackbox-tests/test-cases/merlin/suffix.t/dune-project
@@ -0,0 +1,15 @@
+(lang dune 2.8)
+
+(dialect
+ (name altercaml)
+ (implementation
+  (extension aml))
+ (interface
+  (extension amli)))
+
+(dialect
+ (name betteraltercaml)
+ (implementation
+  (extension baml))
+ (interface
+  (extension bamli)))
diff --git a/test/blackbox-tests/test-cases/merlin/suffix.t/run.t b/test/blackbox-tests/test-cases/merlin/suffix.t/run.t
new file mode 100644
index 00000000000..f688a79955e
--- /dev/null
+++ b/test/blackbox-tests/test-cases/merlin/suffix.t/run.t
@@ -0,0 +1,5 @@
+  $ dune build @check
+
+  $ cat .merlin | grep SUFFIX
+  SUFFIX .aml .amli
+  SUFFIX .baml .bamli