Cartopy: show tick marks of axes

Question

I want to show axes tick marks outside. Cartopy removes axes tick marks!. I tried the solution here.

import matplotlib.pyplot as plt
import cartopy.crs as ccrs

from cartopy.mpl.ticker import (LongitudeFormatter, LatitudeFormatter,
                                LatitudeLocator, LongitudeLocator)

fig, ax = plt.subplots(figsize=(10, 5), subplot_kw={"projection":ccrs.PlateCarree()})

ax.coastlines()

gl = ax.gridlines(crs=ccrs.PlateCarree(), draw_labels=True,
                  linewidth=2, color='gray', alpha=0.5, linestyle='--')
gl.top_labels = False
gl.left_labels = False


gl.xlocator = LongitudeLocator()
gl.ylocator = LatitudeLocator()
gl.xformatter = LongitudeFormatter(auto_hide=False)
gl.yformatter = LatitudeFormatter()

ax.tick_params(axis="both",
               tickdir='out',
               length=15,
               grid_transform=ccrs.PlateCarree()) # this did not work

gl.axes.tick_params(axis="both",
               tickdir='out',
               length=15,
               grid_transform=ccrs.PlateCarree()) # this also did not work

plt.show()