diff --git a/crates/cli-support/src/js/js2rust.rs b/crates/cli-support/src/js/js2rust.rs
index 4fe8c303..771055fd 100644
--- a/crates/cli-support/src/js/js2rust.rs
+++ b/crates/cli-support/src/js/js2rust.rs
@@ -68,6 +68,9 @@ pub struct Js2Rust<'a, 'b: 'a> {
     /// The string value here is the class that this should be a constructor
     /// for.
     constructor: Option<String>,
+
+    /// whether or not we're generating a method
+    method: bool,
 }
 
 impl<'a, 'b> Js2Rust<'a, 'b> {
@@ -83,6 +86,7 @@ impl<'a, 'b> Js2Rust<'a, 'b> {
             ret_ty: String::new(),
             ret_expr: String::new(),
             constructor: None,
+            method: false,
         }
     }
 
@@ -93,12 +97,19 @@ impl<'a, 'b> Js2Rust<'a, 'b> {
         function: &Function,
         opt_arg_names: &Option<Vec<String>>,
     ) -> Result<&mut Self, Error> {
+        // Chop off the implicit i32 first argument if we're a method since it
+        // was already handled by `method` below.
+        let arguments = if self.method {
+            &function.arguments[1..]
+        } else {
+            &function.arguments[..]
+        };
         let arg_names = match opt_arg_names {
             Some(arg_names) => arg_names.iter().map(|s| Some(s.as_str())).collect(),
-            None => vec![None; function.arguments.len()],
+            None => vec![None; arguments.len()],
         };
-        assert_eq!(arg_names.len(), function.arguments.len());
-        for (arg, arg_name) in function.arguments.iter().zip(arg_names) {
+        assert_eq!(arg_names.len(), arguments.len());
+        for (arg, arg_name) in arguments.iter().zip(arg_names) {
             // Process the function argument and assert that the metadata about
             // the number of arguments on the Rust side required is correct.
             let before = self.rust_arguments.len();
@@ -124,6 +135,7 @@ impl<'a, 'b> Js2Rust<'a, 'b> {
     /// Flag this shim as a method call into Rust, so the first Rust argument
     /// passed should be `this.ptr`.
     pub fn method(&mut self, consumed: bool) -> &mut Self {
+        self.method = true;
         if self.cx.config.debug {
             self.prelude(
                 "if (this.ptr === 0) {
diff --git a/crates/cli-support/src/webidl.rs b/crates/cli-support/src/webidl.rs
index 0409e39a..c8913cda 100644
--- a/crates/cli-support/src/webidl.rs
+++ b/crates/cli-support/src/webidl.rs
@@ -580,7 +580,7 @@ impl<'a> Context<'a> {
             Some(class) => struct_function_export_name(class, export.function.name),
             None => export.function.name.to_string(),
         };
-        let descriptor = match self.descriptors.remove(&wasm_name) {
+        let mut descriptor = match self.descriptors.remove(&wasm_name) {
             None => return Ok(()),
             Some(d) => d.unwrap_function(),
         };
@@ -595,23 +595,32 @@ impl<'a> Context<'a> {
                 match export.method_kind {
                     decode::MethodKind::Constructor => AuxExportKind::Constructor(class),
                     decode::MethodKind::Operation(op) => match op.kind {
-                        decode::OperationKind::Getter(f) => AuxExportKind::Getter {
-                            class,
-                            field: f.to_string(),
-                        },
-                        decode::OperationKind::Setter(f) => AuxExportKind::Setter {
-                            class,
-                            field: f.to_string(),
-                        },
+                        decode::OperationKind::Getter(f) => {
+                            descriptor.arguments.insert(0, Descriptor::I32);
+                            AuxExportKind::Getter {
+                                class,
+                                field: f.to_string(),
+                            }
+                        }
+                        decode::OperationKind::Setter(f) => {
+                            descriptor.arguments.insert(0, Descriptor::I32);
+                            AuxExportKind::Setter {
+                                class,
+                                field: f.to_string(),
+                            }
+                        }
                         _ if op.is_static => AuxExportKind::StaticFunction {
                             class,
                             name: export.function.name.to_string(),
                         },
-                        _ => AuxExportKind::Method {
-                            class,
-                            name: export.function.name.to_string(),
-                            consumed: export.consumed,
-                        },
+                        _ => {
+                            descriptor.arguments.insert(0, Descriptor::I32);
+                            AuxExportKind::Method {
+                                class,
+                                name: export.function.name.to_string(),
+                                consumed: export.consumed,
+                            }
+                        }
                     },
                 }
             }
@@ -931,7 +940,7 @@ impl<'a> Context<'a> {
             // Register a webidl transformation for the getter
             let (getter_id, _) = self.function_exports[&getter];
             let getter_descriptor = Function {
-                arguments: Vec::new(),
+                arguments: vec![Descriptor::I32],
                 shim_idx: 0,
                 ret: descriptor.clone(),
             };
@@ -956,7 +965,7 @@ impl<'a> Context<'a> {
 
             let (setter_id, _) = self.function_exports[&setter];
             let setter_descriptor = Function {
-                arguments: vec![descriptor],
+                arguments: vec![Descriptor::I32, descriptor],
                 shim_idx: 0,
                 ret: Descriptor::Unit,
             };