diff --git a/platformio/builder/tools/piosize.py b/platformio/builder/tools/piosize.py
index dd6ec357..533e22ab 100644
--- a/platformio/builder/tools/piosize.py
+++ b/platformio/builder/tools/piosize.py
@@ -12,6 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# pylint: disable=too-many-locals
+
 from __future__ import absolute_import
 
 import sys
@@ -23,12 +25,14 @@ from elftools.elf.elffile import ELFFile
 
 from platformio.compat import dump_json_to_unicode
 from platformio.proc import exec_command
+from platformio.util import get_systype
 
 
 def _get_file_location(env, elf_path, addr, sysenv):
     cmd = [env.subst("$CC").replace("-gcc", "-addr2line"), "-e", elf_path, hex(addr)]
     result = exec_command(cmd, env=sysenv)
-    return result["out"].strip().replace("\\", "/")
+    path = result["out"].strip()
+    return path.replace("/", "\\") if "windows" in get_systype() else path
 
 
 def _determine_section(sections, symbol_addr):