diff --git a/src/symbolic/symbolic_wasm_ffi.ml b/src/symbolic/symbolic_wasm_ffi.ml
index 36a920c5a..16e150898 100644
--- a/src/symbolic/symbolic_wasm_ffi.ml
+++ b/src/symbolic/symbolic_wasm_ffi.ml
@@ -115,17 +115,21 @@ module M :
         make_str_null_terminated m (ch :: accu) (Int32.add i (Int32.of_int 1))
     | _ -> assert false
 
-  let rec make_str_of_length m accu i len =
-    let open Symbolic_choice in
-    if len < i then return (List.rev accu |> Array.of_list)
-    else
-      let* p = Symbolic_memory.load_8_u m (Symbolic_i32.of_int i) in
-      match Smtml.Typed.view p with
-      | Val (Bitv bv) when Smtml.Bitvector.numbits bv = 32 ->
-        let c = Smtml.Bitvector.to_int32 bv in
-        let ch = char_of_int (Int32.to_int c) in
-        make_str_of_length m (ch :: accu) (succ i) len
-      | _ -> assert false
+  let make_str_of_length ~mem ~ptr ~len =
+    let rec aux acc i =
+      let open Symbolic_choice in
+      if i >= len then return (List.rev acc |> Array.of_list)
+      else
+        let* p = Symbolic_memory.load_8_u mem (Symbolic_i32.of_int (ptr + i)) in
+        match Smtml.Typed.view p with
+        | Val (Bitv bv) when Smtml.Bitvector.numbits bv = 32 ->
+          let c = Smtml.Bitvector.to_int32 bv in
+          let ch = char_of_int (Int32.to_int c) in
+          let i = succ i in
+          aux (ch :: acc) i
+        | _ -> assert false
+    in
+    aux [] 0
 
   let cov_label_is_covered id =
     let open Symbolic_choice in
@@ -166,13 +170,13 @@ module M :
     let str = String.init (Array.length chars) (Array.get chars) in
     open_scope str
 
-  let open_scope_of_length m ptr len =
+  let open_scope_of_length mem ptr len =
     let open Symbolic_choice in
     let* ptr = select_i32 ptr in
     let ptr = Int32.to_int ptr in
     let* len = select_i32 len in
     let len = Int32.to_int len in
-    let* bytes = make_str_of_length m [] ptr len in
+    let* bytes = make_str_of_length ~mem ~ptr ~len in
     let str = String.init len (Array.get bytes) in
     open_scope str
 
diff --git a/test/rust/basic_named_symbol.t/f.rs b/test/rust/basic_named_symbol.t/f.rs
new file mode 100644
index 000000000..ce79163a7
--- /dev/null
+++ b/test/rust/basic_named_symbol.t/f.rs
@@ -0,0 +1,15 @@
+use owi_sym::Symbolic;
+
+fn mean1(x: i32, y: i32) -> i32 {
+    (x + y) / 2
+}
+
+fn mean2(x: i32, y: i32) -> i32 {
+    (x & y) + ((x ^ y) >> 1)
+}
+
+fn main() {
+    let x = i32::named_symbol("x");
+    let y = i32::named_symbol("y");
+    owi_sym::assert(mean1(x, y) == mean2(x, y))
+}
diff --git a/test/rust/basic_named_symbol.t/run.t b/test/rust/basic_named_symbol.t/run.t
new file mode 100644
index 000000000..b6497c00f
--- /dev/null
+++ b/test/rust/basic_named_symbol.t/run.t
@@ -0,0 +1,8 @@
+  $ owi rust ./f.rs -w1
+  owi: [ERROR] Trap: unreachable
+  model {
+    symbol symbol_0 i32 -1816735914 x
+    symbol symbol_1 i32 -1802216685 y
+  }
+  owi: [ERROR] Reached problem!
+  [13]