diff --git a/src/AstGen.zig b/src/AstGen.zig
index 000151a2cc31c9269403bc619487a1c24810aa99..749e3d28c461bddcf69e91ce08ebae6c14d6441b 100644
--- a/src/AstGen.zig
+++ b/src/AstGen.zig
@@ -2906,9 +2906,14 @@ fn deferStmt(
         try gz.addDbgBlockBegin();
         const ident_name = try gz.astgen.identAsString(payload_token);
         remapped_err_code = @intCast(Zir.Inst.Index, gz.astgen.instructions.len);
-        // Use a placeholder tag of .as to allow querying things that depend on the tag,
-        // but undefined data to prevent querying of data.bin.
-        try gz.astgen.instructions.append(gz.astgen.gpa, .{ .tag = .as, .data = undefined });
+        try gz.astgen.instructions.append(gz.astgen.gpa, .{
+            .tag = .extended,
+            .data = .{ .extended = .{
+                .opcode = .errdefer_err_code,
+                .small = undefined,
+                .operand = undefined,
+            } },
+        });
         const remapped_err_code_ref = Zir.indexToRef(remapped_err_code);
         local_val_scope = .{
             .parent = &defer_gen.base,
diff --git a/src/Sema.zig b/src/Sema.zig
index 13f4d684a151cb46c1f89f7d0a76b41f9a873e45..b2387dfe12ba1b375838ab6bf0a04fb479e80776 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -1198,6 +1198,7 @@ fn analyzeBodyInner(
                         i += 1;
                         continue;
                     },
+                    .errdefer_err_code => unreachable, // never appears in a body
                 };
             },
 
diff --git a/src/Zir.zig b/src/Zir.zig
index 51c90c61cbc68a2438aae40df8b44649660ae78a..7f9681e5333684c99553c2886cf3372d0b99141f 100644
--- a/src/Zir.zig
+++ b/src/Zir.zig
@@ -1979,7 +1979,7 @@ pub const Inst = struct {
         /// `operand` is `src_node: i32`.
         breakpoint,
         /// Implements the `@select` builtin.
-        /// operand` is payload index to `Select`.
+        /// `operand` is payload index to `Select`.
         select,
         /// Implement builtin `@errToInt`.
         /// `operand` is payload index to `UnNode`.
@@ -1999,7 +1999,7 @@ pub const Inst = struct {
         /// `operand` is payload index to `Cmpxchg`.
         cmpxchg,
         /// Implement the builtin `@addrSpaceCast`
-        /// `Operand` is payload index to `BinNode`. `lhs` is dest type, `rhs` is operand.
+        /// `operand` is payload index to `BinNode`. `lhs` is dest type, `rhs` is operand.
         addrspace_cast,
         /// Implement builtin `@cVaArg`.
         /// `operand` is payload index to `BinNode`.
@@ -2031,6 +2031,9 @@ pub const Inst = struct {
         /// Implements the `@inComptime` builtin.
         /// `operand` is `src_node: i32`.
         in_comptime,
+        /// Used as a placeholder for the capture of an `errdefer`.
+        /// This is replaced by Sema with the captured value.
+        errdefer_err_code,
 
         pub const InstData = struct {
             opcode: Extended,
diff --git a/src/print_zir.zig b/src/print_zir.zig
index 4e4f13641c3351f368e0b9ff52dd0be8b00d7c66..f228adc7ea7fc086dd3119473254e273a05545b8 100644
--- a/src/print_zir.zig
+++ b/src/print_zir.zig
@@ -467,6 +467,7 @@ const Writer = struct {
             .breakpoint,
             .c_va_start,
             .in_comptime,
+            .errdefer_err_code,
             => try self.writeExtNode(stream, extended),
 
             .builtin_src => {