diff --git a/src/dune_rules/cram_exec.ml b/src/dune_rules/cram_exec.ml
index 2adb9c76526..4c74f59b231 100644
--- a/src/dune_rules/cram_exec.ml
+++ b/src/dune_rules/cram_exec.ml
@@ -111,16 +111,39 @@ let translate_path_for_sh =
    On Windows, we still generate a [sh] script so we need to quote using Unix
    conventions. *)
 let quote_for_sh fn =
-  (* we lose some portability as [$'] isn't posix. I don't see a better way to
-     do this *)
-  let buf = Buffer.create (String.length fn + 2) in
-  Buffer.add_string buf "$'";
+  (* we lose some portability as [$'] isn't posix. This is why we prefer single
+     quotes when possible *)
+  let has_single_quote = ref false in
+  (* minimum chars for [$'']*)
+  let posix_quote_len = ref 3 in
   String.iter fn ~f:(function
-    | '\'' -> Buffer.add_string buf "\'"
-    | '\\' -> Buffer.add_string buf "\\\\"
-    | c -> Buffer.add_char buf c);
-  Buffer.add_char buf '\'';
-  Buffer.contents buf
+    | '\'' ->
+      posix_quote_len := !posix_quote_len + 2;
+      has_single_quote := true
+    | '\\' -> posix_quote_len := !posix_quote_len + 2
+    | _ -> incr posix_quote_len);
+  match !has_single_quote with
+  | false -> "'" ^ fn ^ "'"
+  | true ->
+    let len = !posix_quote_len in
+    let res = Bytes.create len in
+    Bytes.set res 0 '$';
+    Bytes.set res 1 '\'';
+    Bytes.set res (len - 1) '\'';
+    let i = ref 2 in
+    String.iter fn ~f:(function
+      | '\'' ->
+        Bytes.set res !i '\\';
+        Bytes.set res (!i + 1) '\'';
+        i := !i + 2
+      | '\\' ->
+        Bytes.set res !i '\\';
+        Bytes.set res (!i + 1) '\\';
+        i := !i + 2
+      | c ->
+        Bytes.set res !i c;
+        incr i);
+    Bytes.to_string res
 
 let cram_stanzas lexbuf =
   let rec loop acc =