diff --git a/fs_mgr/liblp/builder.cpp b/fs_mgr/liblp/builder.cpp
index 4406696ae..7e7f39370 100644
--- a/fs_mgr/liblp/builder.cpp
+++ b/fs_mgr/liblp/builder.cpp
@@ -1125,6 +1125,11 @@ void MetadataBuilder::SetAutoSlotSuffixing() {
     auto_slot_suffixing_ = true;
 }
 
+void MetadataBuilder::SetVirtualABDeviceFlag() {
+    RequireExpandedMetadataHeader();
+    header_.flags |= LP_HEADER_FLAG_VIRTUAL_AB_DEVICE;
+}
+
 bool MetadataBuilder::IsABDevice() {
     return !IPropertyFetcher::GetInstance()->GetProperty("ro.boot.slot_suffix", "").empty();
 }
diff --git a/fs_mgr/liblp/include/liblp/builder.h b/fs_mgr/liblp/include/liblp/builder.h
index 7a334fbd9..851f04180 100644
--- a/fs_mgr/liblp/include/liblp/builder.h
+++ b/fs_mgr/liblp/include/liblp/builder.h
@@ -318,6 +318,8 @@ class MetadataBuilder {
 
     // Set the LP_METADATA_AUTO_SLOT_SUFFIXING flag.
     void SetAutoSlotSuffixing();
+    // Set the LP_HEADER_FLAG_VIRTUAL_AB_DEVICE flag.
+    void SetVirtualABDeviceFlag();
 
     // If set, checks for slot suffixes will be ignored internally.
     void IgnoreSlotSuffixing();
diff --git a/fs_mgr/liblp/include/liblp/metadata_format.h b/fs_mgr/liblp/include/liblp/metadata_format.h
index 26cbf07ba..d3c98748d 100644
--- a/fs_mgr/liblp/include/liblp/metadata_format.h
+++ b/fs_mgr/liblp/include/liblp/metadata_format.h
@@ -224,8 +224,6 @@ typedef struct LpMetadataHeader {
     /* 128: See LP_HEADER_FLAG_ constants for possible values. Header flags are
      * independent of the version number and intended to be informational only.
      * New flags can be added without bumping the version.
-     *
-     * (Note there are no flags currently defined.)
      */
     uint32_t flags;
 
@@ -233,6 +231,11 @@ typedef struct LpMetadataHeader {
     uint8_t reserved[124];
 } __attribute__((packed)) LpMetadataHeader;
 
+/* This device uses Virtual A/B. Note that on retrofit devices, the expanded
+ * header may not be present.
+ */
+#define LP_HEADER_FLAG_VIRTUAL_AB_DEVICE 0x1
+
 /* This struct defines a logical partition entry, similar to what would be
  * present in a GUID Partition Table.
  */