diff --git a/extendedcommands.c b/extendedcommands.c
index 64c4e3d..c2a0e18 100644
--- a/extendedcommands.c
+++ b/extendedcommands.c
@@ -423,8 +423,7 @@ int format_unknown_device(const char *device, const char* path, const char *fs_t
 {
     LOGI("Formatting unknown device.\n");
 
-    // device may simply be a name, like "system"
-    if (get_flash_type(fs_type) != UNSUPPORTED)
+    if (fs_type != NULL && get_flash_type(fs_type) != UNSUPPORTED)
         return erase_raw_partition(fs_type, device);
 
     // if this is SDEXT:, don't worry about it if it does not exist.