diff --git a/crates/fuzzing/src/oracles.rs b/crates/fuzzing/src/oracles.rs
index 38f355c36f..7d07117c8b 100644
--- a/crates/fuzzing/src/oracles.rs
+++ b/crates/fuzzing/src/oracles.rs
@@ -16,6 +16,7 @@ use crate::generators;
 use arbitrary::Arbitrary;
 use log::debug;
 use std::cell::Cell;
+use std::convert::TryInto;
 use std::rc::Rc;
 use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};
 use std::sync::{Arc, Condvar, Mutex};
@@ -843,7 +844,14 @@ pub fn differential_spec_execution(wasm: &[u8], config: &generators::Config) ->
             (wasm_spec_interpreter::Value::F64(a), wasmtime::Val::F64(b)) => {
                 f64_equal(*a as u64, *b)
             }
-            (_, _) => unreachable!("fuzzing non-scalar value types is still TODO"),
+            (wasm_spec_interpreter::Value::V128(a), wasmtime::Val::V128(b)) => {
+                assert_eq!(a.len(), 16);
+                let a_num = u128::from_le_bytes(a.as_slice().try_into().unwrap());
+                a_num == *b
+            }
+            (_, _) => {
+                unreachable!("TODO: only fuzzing of scalar and vector value types is supported")
+            }
         }
     }
 
diff --git a/crates/fuzzing/wasm-spec-interpreter/build.rs b/crates/fuzzing/wasm-spec-interpreter/build.rs
index 61d5986c70..472ec0165c 100644
--- a/crates/fuzzing/wasm-spec-interpreter/build.rs
+++ b/crates/fuzzing/wasm-spec-interpreter/build.rs
@@ -12,7 +12,7 @@ const OCAML_DIR: &'static str = "ocaml";
 const SPEC_DIR: &'static str = "ocaml/spec";
 const SPEC_REPOSITORY: &'static str = "https://github.com/conrad-watt/spec";
 const SPEC_REPOSITORY_BRANCH: &'static str = "wasmtime_fuzzing";
-const SPEC_REPOSITORY_REV: &'static str = "7485eb0084b74871f96f261b9f916864596d8f1d";
+const SPEC_REPOSITORY_REV: &'static str = "52851c8394ee4099fb8bdeaec6d60d92e787052f";
 
 fn main() {
     if cfg!(feature = "build-libinterpret") {
diff --git a/crates/fuzzing/wasm-spec-interpreter/ocaml/README.md b/crates/fuzzing/wasm-spec-interpreter/ocaml/README.md
index 21cfb7c373..58888d97e4 100644
--- a/crates/fuzzing/wasm-spec-interpreter/ocaml/README.md
+++ b/crates/fuzzing/wasm-spec-interpreter/ocaml/README.md
@@ -1,7 +1,7 @@
 This directory contains the necessary parts for building a library with FFI
 access to the Wasm spec interpreter. Its major parts:
  - `spec`: the Wasm spec code as a Git submodule (you may need to retrieve it:
-   `git clone https://github.com/conrad-watt/spec/tree/wasmtime_fuzzing).
+   `git clone -b wasmtime_fuzzing https://github.com/conrad-watt/spec`).
  - `interpret.ml`: a shim layer for calling the Wasm spec code and exposing it
    for FFI access
  - `Makefile`: the steps for gluing these pieces together into a static library
diff --git a/crates/fuzzing/wasm-spec-interpreter/ocaml/interpret.ml b/crates/fuzzing/wasm-spec-interpreter/ocaml/interpret.ml
index cda7ea2032..04098607e2 100644
--- a/crates/fuzzing/wasm-spec-interpreter/ocaml/interpret.ml
+++ b/crates/fuzzing/wasm-spec-interpreter/ocaml/interpret.ml
@@ -16,20 +16,23 @@ type ffi_value =
   | I64 of int64
   | F32 of int32
   | F64 of int64
+  | V128 of Bytes.t
 
 (** Helper for converting the FFI values to their spec interpreter type. *)
 let convert_to_wasm (v: ffi_value) : v = match v with
-| I32 n -> ConstInt32 (I32_impl_abs n)
-| I64 n -> ConstInt64 (I64_impl_abs n)
-| F32 n -> ConstFloat32 (F32.of_bits n)
-| F64 n -> ConstFloat64 (F64.of_bits n)
+| I32 n -> V_num (ConstInt32 (I32_impl_abs n))
+| I64 n -> V_num (ConstInt64 (I64_impl_abs n))
+| F32 n -> V_num (ConstFloat32 (F32.of_bits n))
+| F64 n -> V_num (ConstFloat64 (F64.of_bits n))
+| V128 n -> V_vec (ConstVec128 (V128.of_bits (Bytes.to_string n)))
 
 (** Helper for converting the spec interpreter values to their FFI type. *)
 let convert_from_wasm (v: v) : ffi_value = match v with
-| (ConstInt32 (I32_impl_abs n)) -> I32 n
-| (ConstInt64 (I64_impl_abs n)) -> I64 n
-| (ConstFloat32 n) -> F32 (F32.to_bits n)
-| (ConstFloat64 n) -> F64 (F64.to_bits n)
+| V_num ((ConstInt32 (I32_impl_abs n))) -> I32 n
+| V_num ((ConstInt64 (I64_impl_abs n))) -> I64 n
+| V_num ((ConstFloat32 n)) -> F32 (F32.to_bits n)
+| V_num ((ConstFloat64 n)) -> F64 (F64.to_bits n)
+| V_vec ((ConstVec128 n)) -> V128 (Bytes.of_string (V128.to_bits n))
 | _ -> failwith "Unknown type"
 
 (** Parse the given WebAssembly module binary into an Ast.module_. At some point in the future this
diff --git a/crates/fuzzing/wasm-spec-interpreter/src/lib.rs b/crates/fuzzing/wasm-spec-interpreter/src/lib.rs
index a2f46a3a9a..6a977f7f50 100644
--- a/crates/fuzzing/wasm-spec-interpreter/src/lib.rs
+++ b/crates/fuzzing/wasm-spec-interpreter/src/lib.rs
@@ -16,6 +16,7 @@ pub enum Value {
     I64(i64),
     F32(i32),
     F64(i64),
+    V128(Vec<u8>),
 }
 
 #[cfg(feature = "has-libinterpret")]
diff --git a/crates/fuzzing/wasm-spec-interpreter/src/with_library.rs b/crates/fuzzing/wasm-spec-interpreter/src/with_library.rs
index 9dadce4866..81806f61b3 100644
--- a/crates/fuzzing/wasm-spec-interpreter/src/with_library.rs
+++ b/crates/fuzzing/wasm-spec-interpreter/src/with_library.rs
@@ -59,6 +59,7 @@ mod ocaml_bindings {
             Value::I64(i: OCamlInt64),
             Value::F32(i: OCamlInt32),
             Value::F64(i: OCamlInt64),
+            Value::V128(i: OCamlBytes),
         }
     }
 
@@ -103,4 +104,21 @@ mod tests {
             Err("Error(_, \"(Isabelle) trap: load\")".to_string())
         );
     }
+
+    #[test]
+    fn simd_not() {
+        let module = wat::parse_file("tests/simd_not.wat").unwrap();
+
+        let parameters = Some(vec![Value::V128(vec![
+            0, 255, 0, 0, 255, 0, 0, 0, 0, 255, 0, 0, 0, 0, 0, 0,
+        ])]);
+        let results = interpret(&module, parameters.clone()).unwrap();
+
+        assert_eq!(
+            results,
+            vec![Value::V128(vec![
+                255, 0, 255, 255, 0, 255, 255, 255, 255, 0, 255, 255, 255, 255, 255, 255
+            ])]
+        );
+    }
 }
diff --git a/crates/fuzzing/wasm-spec-interpreter/tests/simd_not.wat b/crates/fuzzing/wasm-spec-interpreter/tests/simd_not.wat
new file mode 100644
index 0000000000..6ea48fa14d
--- /dev/null
+++ b/crates/fuzzing/wasm-spec-interpreter/tests/simd_not.wat
@@ -0,0 +1,4 @@
+(module
+  (func (export "simd_not") (param $a v128) (result v128)
+    local.get $a
+    v128.not))
diff --git a/fuzz/fuzz_targets/differential_spec.rs b/fuzz/fuzz_targets/differential_spec.rs
index 6ed13ff16c..1b9fe39c3d 100644
--- a/fuzz/fuzz_targets/differential_spec.rs
+++ b/fuzz/fuzz_targets/differential_spec.rs
@@ -23,6 +23,7 @@ fn run(data: &[u8]) -> Result<()> {
 
     // Enable features that the spec interpreter has implemented
     config.module_config.config.multi_value_enabled = false;
+    config.module_config.config.simd_enabled = true;
 
     // TODO: this is a best-effort attempt to avoid errors caused by the
     //       generated module exporting no functions.