diff --git a/Cargo.lock b/Cargo.lock
index d775bb0bf3..40c405d805 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3280,9 +3280,9 @@ dependencies = [
 
 [[package]]
 name = "serde_v8"
-version = "0.9.0"
+version = "0.9.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "88bf7bf03d60f6c5098d2d1867404ff50695435f638c34e4a95b8b3631cb4900"
+checksum = "f5ce7662cda194ff443bddf146c952e83075889590838cd41df768fba7d152d0"
 dependencies = [
  "rusty_v8",
  "serde",
diff --git a/cli/tests/unit/ffi_test.ts b/cli/tests/unit/ffi_test.ts
new file mode 100644
index 0000000000..ab25df699e
--- /dev/null
+++ b/cli/tests/unit/ffi_test.ts
@@ -0,0 +1,25 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+import { assertThrows, unitTest } from "./test_util.ts";
+
+unitTest(function dlopenInvalidArguments() {
+  const filename = "/usr/lib/libc.so.6";
+  assertThrows(() => {
+    // @ts-expect-error: ForeignFunction cannot be null
+    Deno.dlopen(filename, { malloc: null });
+  }, TypeError);
+  assertThrows(() => {
+    Deno.dlopen(filename, {
+      // @ts-expect-error: invalid NativeType
+      malloc: { parameters: ["a"], result: "b" },
+    });
+  }, TypeError);
+  assertThrows(() => {
+    // @ts-expect-error: DynamicLibrary symbols cannot be null
+    Deno.dlopen(filename, null);
+  }, TypeError);
+  assertThrows(() => {
+    // @ts-expect-error: require 2 arguments
+    Deno.dlopen(filename);
+  }, TypeError);
+});
diff --git a/core/Cargo.toml b/core/Cargo.toml
index 7ddb7d8147..78fbf18368 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -25,7 +25,7 @@ pin-project = "1.0.7"
 rusty_v8 = "0.26.0"
 serde = { version = "1.0.126", features = ["derive"] }
 serde_json = { version = "1.0.64", features = ["preserve_order"] }
-serde_v8 = { version = "0.9.0" }
+serde_v8 = { version = "0.9.3" }
 url = { version = "2.2.2", features = ["serde"] }
 
 [[example]]
diff --git a/ext/ffi/lib.rs b/ext/ffi/lib.rs
index cfff59953e..673f834722 100644
--- a/ext/ffi/lib.rs
+++ b/ext/ffi/lib.rs
@@ -75,12 +75,13 @@ impl DynamicLibraryResource {
   ) -> Result<(), AnyError> {
     let fn_ptr = unsafe { self.lib.symbol::<*const c_void>(&symbol) }?;
     let ptr = libffi::middle::CodePtr::from_ptr(fn_ptr as _);
-    let parameter_types =
-      foreign_fn.parameters.into_iter().map(NativeType::from);
-    let result_type = NativeType::from(foreign_fn.result);
     let cif = libffi::middle::Cif::new(
-      parameter_types.clone().map(libffi::middle::Type::from),
-      result_type.into(),
+      foreign_fn
+        .parameters
+        .clone()
+        .into_iter()
+        .map(libffi::middle::Type::from),
+      foreign_fn.result.into(),
     );
 
     self.symbols.insert(
@@ -88,8 +89,8 @@ impl DynamicLibraryResource {
       Symbol {
         cif,
         ptr,
-        parameter_types: parameter_types.collect(),
-        result_type,
+        parameter_types: foreign_fn.parameters,
+        result_type: foreign_fn.result,
       },
     );
 
@@ -153,27 +154,6 @@ impl From<NativeType> for libffi::middle::Type {
   }
 }
 
-impl From<String> for NativeType {
-  fn from(string: String) -> Self {
-    match string.as_str() {
-      "void" => NativeType::Void,
-      "u8" => NativeType::U8,
-      "i8" => NativeType::I8,
-      "u16" => NativeType::U16,
-      "i16" => NativeType::I16,
-      "u32" => NativeType::U32,
-      "i32" => NativeType::I32,
-      "u64" => NativeType::U64,
-      "i64" => NativeType::I64,
-      "usize" => NativeType::USize,
-      "isize" => NativeType::ISize,
-      "f32" => NativeType::F32,
-      "f64" => NativeType::F64,
-      _ => unimplemented!(),
-    }
-  }
-}
-
 #[repr(C)]
 union NativeValue {
   void_value: (),
@@ -279,8 +259,8 @@ fn value_as_f64(value: Value) -> f64 {
 
 #[derive(Deserialize, Debug)]
 struct ForeignFunction {
-  parameters: Vec<String>,
-  result: String,
+  parameters: Vec<NativeType>,
+  result: NativeType,
 }
 
 #[derive(Deserialize, Debug)]