diff --git a/bootstraptest/runner.rb b/bootstraptest/runner.rb
index f8a53aedd8..2cd91ffd07 100755
--- a/bootstraptest/runner.rb
+++ b/bootstraptest/runner.rb
@@ -530,7 +530,9 @@ def cleanup_coredump
     core_path = "/tmp/bootstraptest-core.#{Time.now.utc.iso8601}"
     warn "A core file is found. Saving it at: #{core_path.dump}"
     FileUtils.mv('core', core_path)
-    system('gdb', @ruby, '-c', core_path, '-ex', 'bt', '-batch')
+    cmd = ['gdb', @ruby, '-c', core_path, '-ex', 'bt', '-batch']
+    p cmd # debugging why it's not working
+    system(*cmd)
   end
   FileUtils.rm_f Dir.glob('core.*')
   FileUtils.rm_f @ruby+'.stackdump' if @ruby
diff --git a/tool/lib/test/unit.rb b/tool/lib/test/unit.rb
index b292f25280..d76353cf0f 100644
--- a/tool/lib/test/unit.rb
+++ b/tool/lib/test/unit.rb
@@ -357,7 +357,9 @@ module Test
           core_path = "/tmp/test-unit-core.#{Time.now.utc.iso8601}"
           warn "A core file is found. Saving it at: #{core_path.dump}"
           FileUtils.mv('core', core_path)
-          system('gdb', RbConfig.ruby, '-c', core_path, '-ex', 'bt', '-batch')
+          cmd = ['gdb', RbConfig.ruby, '-c', core_path, '-ex', 'bt', '-batch']
+          p cmd # debugging why it's not working
+          system(*cmd)
         end
         STDERR.flush
         exit c