diff --git a/tests/refc/t18616.nim b/tests/refc/t18616.nim
new file mode 100644
index 0000000000000..6cd6f9307e283
--- /dev/null
+++ b/tests/refc/t18616.nim
@@ -0,0 +1,104 @@
+discard """
+  matrix: "--mm:refc; --mm:arc"
+  joinable: false
+"""
+
+import std/[unittest, asyncdispatch]
+
+# bug #18616
+type
+  ClientResponse = object
+    status*: int
+    data*: string
+
+template asyncTest*(name: string, body: untyped): untyped =
+  test name:
+    waitFor((
+      proc() {.async, gcsafe.} =
+        body
+    )())
+
+suite "Test suite":
+  asyncTest "test1":
+    const PostVectors = [
+      (
+        ("/test/post", "somebody0908", "text/html",
+        "app/type1;q=0.9,app/type2;q=0.8"),
+        ClientResponse(status: 200, data: "type1[text/html,somebody0908]")
+      ),
+      (
+        ("/test/post", "somebody0908", "text/html",
+        "app/type2;q=0.8,app/type1;q=0.9"),
+        ClientResponse(status: 200, data: "type1[text/html,somebody0908]")
+      ),
+      (
+        ("/test/post", "somebody09", "text/html",
+         "app/type2,app/type1;q=0.9"),
+        ClientResponse(status: 200, data: "type2[text/html,somebody09]")
+      ),
+      (
+        ("/test/post", "somebody09", "text/html", "app/type1;q=0.9,app/type2"),
+        ClientResponse(status: 200, data: "type2[text/html,somebody09]")
+      ),
+      (
+        ("/test/post", "somebody", "text/html", "*/*"),
+        ClientResponse(status: 200, data: "type1[text/html,somebody]")
+      ),
+      (
+        ("/test/post", "somebody", "text/html", ""),
+        ClientResponse(status: 200, data: "type1[text/html,somebody]")
+      ),
+      (
+        ("/test/post", "somebody", "text/html", "app/type2"),
+        ClientResponse(status: 200, data: "type2[text/html,somebody]")
+      ),
+      (
+        ("/test/post", "somebody", "text/html", "app/type3"),
+        ClientResponse(status: 406, data: "")
+      )
+    ]
+
+    for item in PostVectors:
+      discard item
+
+  asyncTest "test2":
+    const PostVectors = [
+      (
+        "/test/post", "somebody0908", "text/html",
+        "app/type1;q=0.9,app/type2;q=0.8",
+        ClientResponse(status: 200, data: "type1[text/html,somebody0908]")
+      ),
+      (
+        "/test/post", "somebody0908", "text/html",
+        "app/type2;q=0.8,app/type1;q=0.9",
+        ClientResponse(status: 200, data: "type1[text/html,somebody0908]")
+      ),
+      (
+        "/test/post", "somebody09", "text/html",
+        "app/type2,app/type1;q=0.9",
+        ClientResponse(status: 200, data: "type2[text/html,somebody09]")
+      ),
+      (
+        "/test/post", "somebody09", "text/html", "app/type1;q=0.9,app/type2",
+        ClientResponse(status: 200, data: "type2[text/html,somebody09]")
+      ),
+      (
+        "/test/post", "somebody", "text/html", "*/*",
+        ClientResponse(status: 200, data: "type1[text/html,somebody]")
+      ),
+      (
+        "/test/post", "somebody", "text/html", "",
+        ClientResponse(status: 200, data: "type1[text/html,somebody]")
+      ),
+      (
+        "/test/post", "somebody", "text/html", "app/type2",
+        ClientResponse(status: 200, data: "type2[text/html,somebody]")
+      ),
+      (
+        "/test/post", "somebody", "text/html", "app/type3",
+        ClientResponse(status: 406, data: "")
+      )
+    ]
+
+    for item in PostVectors:
+      discard item
\ No newline at end of file
diff --git a/tests/refc/tsinkbug.nim b/tests/refc/tsinkbug.nim
index de2ec98a54397..2a15f56c0adb4 100644
--- a/tests/refc/tsinkbug.nim
+++ b/tests/refc/tsinkbug.nim
@@ -1,5 +1,5 @@
 discard """
-  matrix: "--gc:refc; --gc:arc"
+  matrix: "--mm:refc; --mm:arc"
   output: '''
 Value is: 42
 Value is: 42'''