diff --git a/bootstraptest/test_insns.rb b/bootstraptest/test_insns.rb
index 3d7f9640a2..1269d7d013 100644
--- a/bootstraptest/test_insns.rb
+++ b/bootstraptest/test_insns.rb
@@ -427,7 +427,6 @@ tests.compact.each do |(insn, expr, *a)|
   end
 end
 
-
 # with trace
 tests.compact.each {|(insn, expr, *a)|
   progn = "set_trace_func(proc{})\n" + expr
diff --git a/gc.c b/gc.c
index 7cc3c53d1a..f4292370a0 100644
--- a/gc.c
+++ b/gc.c
@@ -135,7 +135,7 @@ size_add_overflow(size_t x, size_t y)
 
 #elif defined(DSIZE_T)
     RB_GNUC_EXTENSION DSIZE_T dx = x;
-    RB_GNUC_EXTENSION DSIZE_T dy = x;
+    RB_GNUC_EXTENSION DSIZE_T dy = y;
     RB_GNUC_EXTENSION DSIZE_T dz = dx + dy;
     p = dz > SIZE_MAX;
     z = (size_t)dz;