diff --git a/src/arch/x86_64/CodeGen.zig b/src/arch/x86_64/CodeGen.zig
index da98c1c90124da3a71f92fb893ffada6dea9bf68..79e5c88050d32597736f112afd0d7b5b4e175ae0 100644
--- a/src/arch/x86_64/CodeGen.zig
+++ b/src/arch/x86_64/CodeGen.zig
@@ -5688,7 +5688,7 @@ fn genTypedValue(self: *Self, typed_value: TypedValue) InnerError!MCValue {
                     .val = typed_value.val,
                 });
             } else if (typed_value.ty.abiSize(self.target.*) == 1) {
-                return MCValue{ .immediate = @boolToInt(typed_value.val.isNull()) };
+                return MCValue{ .immediate = @boolToInt(!typed_value.val.isNull()) };
             }
         },
         .Enum => {
diff --git a/test/behavior/cast.zig b/test/behavior/cast.zig
index 9bdb0f35f63a9d4fb174f101f264b07952a60ea3..60eacfee5d36288c1853120f71a62db7ed03273c 100644
--- a/test/behavior/cast.zig
+++ b/test/behavior/cast.zig
@@ -179,7 +179,7 @@ test "@floatCast comptime_int and comptime_float" {
 
 test "coerce undefined to optional" {
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_x86_64 or builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
 
     try expect(MakeType(void).getNull() == null);
     try expect(MakeType(void).getNonNull() != null);