diff --git a/core/fmt.odin b/core/fmt.odin
index ceae65e82..ae2d340e8 100644
--- a/core/fmt.odin
+++ b/core/fmt.odin
@@ -498,7 +498,7 @@ _write_int :: proc(fi: ^Fmt_Info, u: u64, base: int, is_signed: bool, bit_size:
 	}
 
 	match base {
-	case 2, 8, 10, 16:
+	case 2, 8, 10, 12, 16:
 		break;
 	default:
 		panic("_write_int: unknown base, whoops");
diff --git a/core/strconv.odin b/core/strconv.odin
index 5710e76de..5a14d6660 100644
--- a/core/strconv.odin
+++ b/core/strconv.odin
@@ -342,6 +342,7 @@ append_bits :: proc(buf: []byte, u: u64, base: int, is_signed: bool, bit_size: i
 		case 2:  i--; a[i] = 'b';
 		case 8:  i--; a[i] = 'o';
 		case 10: i--; a[i] = 'd';
+		case 12: i--; a[i] = 'z';
 		case 16: i--; a[i] = 'x';
 		default: ok = false;
 		}