diff --git a/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/dune b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/dune
new file mode 100644
index 00000000000..ba0793a2d69
--- /dev/null
+++ b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/dune
@@ -0,0 +1,11 @@
+(melange.emit
+ (target output)
+ (emit_stdlib false)
+ (libraries bar impl2)
+ (modules foo))
+
+(library
+ (name bar)
+ (libraries impl1)
+ (modes melange)
+ (modules))
diff --git a/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/dune-project b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/dune-project
new file mode 100644
index 00000000000..f40bf8c4a59
--- /dev/null
+++ b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/dune-project
@@ -0,0 +1,3 @@
+(lang dune 3.8)
+
+(using melange 0.1)
diff --git a/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/foo.ml b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/foo.ml
new file mode 100644
index 00000000000..2c0468504bc
--- /dev/null
+++ b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/foo.ml
@@ -0,0 +1 @@
+let () = print_endline "should not run"
diff --git a/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl1/dune b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl1/dune
new file mode 100644
index 00000000000..37b89bac081
--- /dev/null
+++ b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl1/dune
@@ -0,0 +1,4 @@
+(library
+ (name impl1)
+ (modes melange)
+ (implements vlib))
diff --git a/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl1/vlib.ml b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl1/vlib.ml
new file mode 100644
index 00000000000..bd1a42a6e85
--- /dev/null
+++ b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl1/vlib.ml
@@ -0,0 +1 @@
+let run () = print_endline "impl1"
diff --git a/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl2/dune b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl2/dune
new file mode 100644
index 00000000000..437c5ecca98
--- /dev/null
+++ b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl2/dune
@@ -0,0 +1,4 @@
+(library
+ (name impl2)
+ (modes melange)
+ (implements vlib))
diff --git a/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl2/vlib.ml b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl2/vlib.ml
new file mode 100644
index 00000000000..bd1a42a6e85
--- /dev/null
+++ b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/impl2/vlib.ml
@@ -0,0 +1 @@
+let run () = print_endline "impl1"
diff --git a/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/run.t b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/run.t
new file mode 100644
index 00000000000..4ce28697c44
--- /dev/null
+++ b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/run.t
@@ -0,0 +1,21 @@
+`melange.emit` that tries to use two implementations for the same virtual lib
+
+  $ dune build @melange
+  Error: Conflicting implementations for virtual library "vlib" in
+  _build/default/vlib:
+  - "impl1" in _build/default/impl1
+    -> required by library "bar" in _build/default
+  - "impl2" in _build/default/impl2
+  This cannot work.
+  -> required by melange target output
+  -> required by alias melange
+  Error: Conflicting implementations for virtual library "vlib" in
+  _build/default/vlib:
+  - "impl1" in _build/default/impl1
+    -> required by library "bar" in _build/default
+  - "impl2" in _build/default/impl2
+  This cannot work.
+  -> required by melange target output
+  -> required by _build/default/output/foo.js
+  -> required by alias melange
+  [1]
diff --git a/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/vlib/dune b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/vlib/dune
new file mode 100644
index 00000000000..ad2e731d3f5
--- /dev/null
+++ b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/vlib/dune
@@ -0,0 +1,4 @@
+(library
+ (name vlib)
+ (modes melange)
+ (virtual_modules vlib))
diff --git a/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/vlib/vlib.mli b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/vlib/vlib.mli
new file mode 100644
index 00000000000..733b2a32313
--- /dev/null
+++ b/test/blackbox-tests/test-cases/melange/double-vlib-impl.t/vlib/vlib.mli
@@ -0,0 +1 @@
+val run : unit -> unit