Fix modifier for `size_t`

1 files changed, 1 insertions, 1 deletions

diff --git a/shape.c b/shape.c
index 2b4256e5f3..24f1394f6c 100644
--- a/shape.c
+++ b/shape.c
@@ -1529,7 +1529,7 @@ Init_default_shapes(void)
     }
 
     if (heaps_count > SHAPE_ID_HEAP_INDEX_MAX) {
-        rb_bug("Init_default_shapes initialized with %lu heaps, only up to %u are supported", heaps_count, SHAPE_ID_HEAP_INDEX_MAX);
+        rb_bug("Init_default_shapes initialized with %zu heaps, only up to %u are supported", heaps_count, SHAPE_ID_HEAP_INDEX_MAX);
     }
 
     size_t index;