Crash in libGLESv2 when running texture-from-pixmap-glesv2 in fallback mode

When running the texture-from-pixmap-glesv2 example:
http://people.canonical.com/~afrantzis/texture-from-pixmap-glesv2/texture-from-pixmap-glesv2.tar.gz
using the fallback texture upload method (using XImage instead of EGLImage) there is a crash in the libGLESv2 library. This happens as soon as the program starts (before any user input) in a call to glTexSubImage2D().

$ gdb --args ./texture_from_pixmap_glesv2 --no-egl-image
GNU gdb (GDB) 7.2-ubuntu
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Reading symbols from /home/alf/work/texture-from-pixmap-glesv2/texture_from_pixmap_glesv2...done.
(gdb) r
Starting program: /home/alf/work/texture-from-pixmap-glesv2/texture_from_pixmap_glesv2 --no-egl-image
[Thread debugging using libthread_db enabled]
EGL extensions: eglCreatePbufferFromClientBuffer EGL_KHR_image EGL_KHR_image_base EGL_KHR_image_pixmap EGL_AMD_create_image
GL extensions: GL_AMD_compressed_3DC_texture GL_AMD_compressed_ATC_texture GL_AMD_performance_monitor GL_AMD_program_binary_Z400 GL_AMD_tiled_rendering GL_EXT_texture_filter_anisotropic GL_EXT_texture_type_2_10_10_10_REV GL_EXT_bgra GL_OES_compressed_ETC1_RGB8_texture GL_OES_compressed_paletted_texture GL_OES_depth_texture GL_OES_depth24 GL_OES_EGL_image GL_OES_EGL_image_external GL_OES_element_index_uint GL_OES_fbo_render_mipmap GL_OES_fragment_precision_high GL_OES_get_program_binary GL_OES_packed_depth_stencil GL_OES_rgb8_rgba8 GL_OES_standard_derivatives GL_OES_texture_3D GL_OES_texture_float GL_OES_texture_half_float GL_OES_texture_half_float_linear GL_OES_texture_npot GL_OES_vertex_half_float GL_OES_vertex_type_10_10_10_2 GL_NV_fence
vertex shader info:
fragment shader info:
info: Link was successful.

==> Draw something on the left with the mouse! <==

Program received signal SIGSEGV, Segmentation fault.
0x2abc14d6 in _rb_tile_with_range_check () from /usr/lib/libGLESv2.so.2.0
(gdb) bt
#0 0x2abc14d6 in _rb_tile_with_range_check () from /usr/lib/libGLESv2.so.2.0
#1 0x2abc14ba in _rb_tile_with_range_check () from /usr/lib/libGLESv2.so.2.0
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb)