diff --git a/extendedcommands.c b/extendedcommands.c
index af67c3e..43d449a 100644
--- a/extendedcommands.c
+++ b/extendedcommands.c
@@ -25,6 +25,7 @@
 #include "cutils/properties.h"
 #include "firmware.h"
 #include "install.h"
+#include "make_ext4fs.h"
 #include "minui/minui.h"
 #include "minzip/DirUtil.h"
 #include "roots.h"
@@ -507,8 +508,13 @@ int format_device(const char *device, const char *path, const char *fs_type) {
     }
 
     if (strcmp(fs_type, "ext4") == 0) {
+        int length = 0;
+        if (strcmp(v->fs_type, "ext4") == 0) {
+            // Our desired filesystem matches the one in fstab, respect v->length
+            length = v->length;
+        }
         reset_ext4fs_info();
-        int result = make_ext4fs(device, NULL, NULL, 0, 0, 0);
+        int result = make_ext4fs(device, length);
         if (result != 0) {
             LOGE("format_volume: make_extf4fs failed on %s\n", device);
             return -1;