diff --git a/src/ir.cpp b/src/ir.cpp
index 5c44e7c0ff..a6686aae76 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -11132,7 +11132,13 @@ static TypeTableEntry *ir_analyze_bit_shift(IrAnalyze *ira, IrInstructionBinOp *
 
 static TypeTableEntry *ir_analyze_bin_op_math(IrAnalyze *ira, IrInstructionBinOp *bin_op_instruction) {
     IrInstruction *op1 = bin_op_instruction->op1->other;
+    if (type_is_invalid(op1->value.type))
+        return ira->codegen->builtin_types.entry_invalid;
+
     IrInstruction *op2 = bin_op_instruction->op2->other;
+    if (type_is_invalid(op2->value.type))
+        return ira->codegen->builtin_types.entry_invalid;
+
     IrBinOp op_id = bin_op_instruction->op_id;
 
     // look for pointer math
@@ -12851,6 +12857,12 @@ static TypeTableEntry *ir_analyze_dereference(IrAnalyze *ira, IrInstructionUnOp
     if (type_is_invalid(ptr_type)) {
         return ira->codegen->builtin_types.entry_invalid;
     } else if (ptr_type->id == TypeTableEntryIdPointer) {
+        if (ptr_type->data.pointer.ptr_len == PtrLenUnknown) {
+            ir_add_error_node(ira, un_op_instruction->base.source_node,
+                buf_sprintf("index syntax required for unknown-length pointer type '%s'",
+                    buf_ptr(&ptr_type->name)));
+            return ira->codegen->builtin_types.entry_invalid;
+        }
         child_type = ptr_type->data.pointer.child_type;
     } else {
         ir_add_error_node(ira, un_op_instruction->base.source_node,
diff --git a/std/special/bootstrap.zig b/std/special/bootstrap.zig
index 64eae79ce4..8aefe4751f 100644
--- a/std/special/bootstrap.zig
+++ b/std/special/bootstrap.zig
@@ -51,7 +51,7 @@ extern fn WinMainCRTStartup() noreturn {
 
 // TODO https://github.com/ziglang/zig/issues/265
 fn posixCallMainAndExit() noreturn {
-    const argc = argc_ptr.*;
+    const argc = argc_ptr[0];
     const argv = @ptrCast([*][*]u8, argc_ptr + 1);
 
     const envp_nullable = @ptrCast([*]?[*]u8, argv + argc + 1);
diff --git a/test/compile_errors.zig b/test/compile_errors.zig
index ab539dd94a..412b2d5fc9 100644
--- a/test/compile_errors.zig
+++ b/test/compile_errors.zig
@@ -1,6 +1,15 @@
 const tests = @import("tests.zig");
 
 pub fn addCases(cases: *tests.CompileErrorContext) void {
+    cases.add(
+        "dereference unknown length pointer",
+        \\export fn entry(x: [*]i32) i32 {
+        \\    return x.*;
+        \\}
+    ,
+        ".tmp_source.zig:2:13: error: index syntax required for unknown-length pointer type '[*]i32'",
+    );
+
     cases.add(
         "field access of unknown length pointer",
         \\const Foo = extern struct {