diff --git a/vlib/builtin/array.v b/vlib/builtin/array.v
index eb95ad457d5759..44eddaf79a5257 100644
--- a/vlib/builtin/array.v
+++ b/vlib/builtin/array.v
@@ -563,13 +563,15 @@ fn (a array) slice(start int, _end int) array {
 	end := if _end == max_int { a.len } else { _end } // max_int
 	$if !no_bounds_checking {
 		if start > end {
-			panic_n2('array.slice: invalid slice index (start>end):', start, end)
+			panic('array.slice: invalid slice index (start>end):' + i64(start).str() + ', ' +
+				i64(end).str())
 		}
 		if end > a.len {
-			panic_n2('array.slice: slice bounds out of range (end>=a.len):', end, a.len)
+			panic('array.slice: slice bounds out of range (' + i64(end).str() + ' >= ' +
+				i64(a.len).str() + ')')
 		}
 		if start < 0 {
-			panic_n('array.slice: slice bounds out of range (start<0):', start)
+			panic('array.slice: slice bounds out of range (start<0):' + start.str())
 		}
 	}
 	// TODO: integrate reference counting
diff --git a/vlib/builtin/builtin.c.v b/vlib/builtin/builtin.c.v
index fa4cb5f9c1e94f..05e851f727445b 100644
--- a/vlib/builtin/builtin.c.v
+++ b/vlib/builtin/builtin.c.v
@@ -769,7 +769,8 @@ pub fn gc_memory_use() usize {
 fn v_fixed_index(i int, len int) int {
 	$if !no_bounds_checking {
 		if i < 0 || i >= len {
-			panic_n2('fixed array index out of range (index, len):', i, len)
+			panic('fixed array index out of range (index: ' + i64(i).str() + ', len: ' +
+				i64(len).str() + ')')
 		}
 	}
 	return i