diff --git a/doc/langref.html.in b/doc/langref.html.in
index 567c12cd0a..28577560e2 100644
--- a/doc/langref.html.in
+++ b/doc/langref.html.in
@@ -5056,7 +5056,7 @@ fn cmpxchgWeakButNotAtomic(comptime T: type, ptr: *T, expected_value: T, new_val
       {#header_close#}
 
       {#header_open|@wasmMemorySize#}
-      <pre>{#syntax#}@wasmMemorySize(index: u32) u32{#endsyntax#}</pre>
+      <pre>{#syntax#}@wasmMemorySize(index: u32) usize{#endsyntax#}</pre>
       <p>
       This function returns the size of the Wasm memory identified by {#syntax#}index{#endsyntax#} as
       an unsigned value in units of Wasm pages. Note that each Wasm page is 64KB in size.
@@ -5070,7 +5070,7 @@ fn cmpxchgWeakButNotAtomic(comptime T: type, ptr: *T, expected_value: T, new_val
       {#header_close#}
 
       {#header_open|@wasmMemoryGrow#}
-      <pre>{#syntax#}@wasmMemoryGrow(index: u32, delta: u32) i32{#endsyntax#}</pre>
+      <pre>{#syntax#}@wasmMemoryGrow(index: u32, delta: usize) isize{#endsyntax#}</pre>
       <p>
       This function increases the size of the Wasm memory identified by {#syntax#}index{#endsyntax#} by
       {#syntax#}delta{#endsyntax#} in units of unsigned number of Wasm pages. Note that each Wasm page
diff --git a/lib/std/zig/AstGen.zig b/lib/std/zig/AstGen.zig
index 905fa4bdc2..ee14d7dee4 100644
--- a/lib/std/zig/AstGen.zig
+++ b/lib/std/zig/AstGen.zig
@@ -9461,7 +9461,7 @@ fn builtinCall(
         },
         .wasm_memory_grow => {
             const index_arg = try comptimeExpr(gz, scope, .{ .rl = .{ .coerced_ty = .u32_type } }, params[0]);
-            const delta_arg = try expr(gz, scope, .{ .rl = .{ .coerced_ty = .u32_type } }, params[1]);
+            const delta_arg = try expr(gz, scope, .{ .rl = .{ .coerced_ty = .usize_type } }, params[1]);
             const result = try gz.addExtendedPayload(.wasm_memory_grow, Zir.Inst.BinNode{
                 .node = gz.nodeIndexToRelative(node),
                 .lhs = index_arg,
diff --git a/src/Air.zig b/src/Air.zig
index 16c20f5a18..9d7016155e 100644
--- a/src/Air.zig
+++ b/src/Air.zig
@@ -782,13 +782,13 @@ pub const Inst = struct {
         field_parent_ptr,
 
         /// Implements @wasmMemorySize builtin.
-        /// Result type is always `u32`,
+        /// Result type is always `usize`,
         /// Uses the `pl_op` field, payload represents the index of the target memory.
         /// The operand is unused and always set to `Ref.none`.
         wasm_memory_size,
 
         /// Implements @wasmMemoryGrow builtin.
-        /// Result type is always `i32`,
+        /// Result type is always `isize`,
         /// Uses the `pl_op` field, payload represents the index of the target memory.
         wasm_memory_grow,
 
@@ -1471,8 +1471,8 @@ pub fn typeOfIndex(air: *const Air, inst: Air.Inst.Index, ip: *const InternPool)
         .save_err_return_trace_index,
         => return Type.usize,
 
-        .wasm_memory_grow => return Type.i32,
-        .wasm_memory_size => return Type.u32,
+        .wasm_memory_grow => return Type.isize,
+        .wasm_memory_size => return Type.usize,
 
         .int_from_bool => return Type.u1,
 
diff --git a/src/Sema.zig b/src/Sema.zig
index 7a1885d652..ca6d562eef 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -26253,7 +26253,7 @@ fn zirWasmMemoryGrow(
     const index: u32 = @intCast(try sema.resolveInt(block, index_src, extra.lhs, Type.u32, .{
         .needed_comptime_reason = "wasm memory size index must be comptime-known",
     }));
-    const delta = try sema.coerce(block, Type.u32, try sema.resolveInst(extra.rhs), delta_src);
+    const delta = try sema.coerce(block, Type.usize, try sema.resolveInst(extra.rhs), delta_src);
 
     try sema.requireRuntimeBlock(block, builtin_src, null);
     return block.addInst(.{
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index 4502fe1c30..9e51417ab6 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -7625,7 +7625,8 @@ pub const FuncGen = struct {
         const o = self.dg.object;
         const pl_op = self.air.instructions.items(.data)[@intFromEnum(inst)].pl_op;
         const index = pl_op.payload;
-        return self.wip.callIntrinsic(.normal, .none, .@"wasm.memory.size", &.{.i32}, &.{
+        const llvm_usize = try o.lowerType(Type.usize);
+        return self.wip.callIntrinsic(.normal, .none, .@"wasm.memory.size", &.{llvm_usize}, &.{
             try o.builder.intValue(.i32, index),
         }, "");
     }
@@ -7634,7 +7635,8 @@ pub const FuncGen = struct {
         const o = self.dg.object;
         const pl_op = self.air.instructions.items(.data)[@intFromEnum(inst)].pl_op;
         const index = pl_op.payload;
-        return self.wip.callIntrinsic(.normal, .none, .@"wasm.memory.grow", &.{.i32}, &.{
+        const llvm_isize = try o.lowerType(Type.isize);
+        return self.wip.callIntrinsic(.normal, .none, .@"wasm.memory.grow", &.{llvm_isize}, &.{
             try o.builder.intValue(.i32, index), try self.resolveInst(pl_op.operand),
         }, "");
     }