diff --git a/src/init.c b/src/init.c
index 97fc76d..d0c22af 100644
--- a/src/init.c
+++ b/src/init.c
@@ -107,6 +107,7 @@ void handle_env_vars()
     debug_thumbnails = getenv("DEBUG_THUMBNAILS") != NULL;
     debug_timers = getenv("DEBUG_TIMERS") != NULL;
     debug_executors = getenv("DEBUG_EXECUTORS") != NULL;
+    thumb_use_shm = getenv("TINT2_THUMBNAIL_SHM") != NULL;
     if (debug_fps) {
         init_fps_distribution();
         char *s = getenv("TRACING_FPS_THRESHOLD");
diff --git a/src/panel.h b/src/panel.h
index cb9bca5..50dbc47 100644
--- a/src/panel.h
+++ b/src/panel.h
@@ -98,6 +98,7 @@ extern gboolean debug_frames;
 extern gboolean debug_thumbnails;
 extern double ui_scale_dpi_ref;
 extern double ui_scale_monitor_size_ref;
+extern gboolean thumb_use_shm;
 
 typedef struct Panel {
     Area area;
diff --git a/src/util/window.c b/src/util/window.c
index a3c6168..40dfd8e 100644
--- a/src/util/window.c
+++ b/src/util/window.c
@@ -578,11 +578,12 @@ gboolean cairo_surface_is_blank(cairo_surface_t *image_surface)
     return empty;
 }
 
+gboolean thumb_use_shm;
+
 cairo_surface_t *get_window_thumbnail(Window win, int size)
 {
     cairo_surface_t *image_surface = NULL;
-    const gboolean shm_allowed = FALSE;
-    if (shm_allowed && server.has_shm && server.composite_manager) {
+    if (thumb_use_shm && server.has_shm && server.composite_manager) {
         image_surface = get_window_thumbnail_ximage(win, (size_t)size, TRUE);
         if (image_surface && cairo_surface_is_blank(image_surface)) {
             cairo_surface_destroy(image_surface);