diff --git a/android/config.go b/android/config.go
index d94a86f..ef8bb66 100644
--- a/android/config.go
+++ b/android/config.go
@@ -1309,6 +1309,22 @@
 	return String(c.productVariables.VendorApiLevel)
 }
 
+func (c *config) PrevVendorApiLevel() string {
+	vendorApiLevel, err := strconv.Atoi(c.VendorApiLevel())
+	if err != nil {
+		panic(fmt.Errorf("Cannot parse vendor API level %s to an integer: %s",
+			c.VendorApiLevel(), err))
+	}
+	if vendorApiLevel < 202404 || vendorApiLevel%100 != 4 {
+		panic("Unknown vendor API level " + c.VendorApiLevel())
+	}
+	// The version before trunk stable is 34.
+	if vendorApiLevel == 202404 {
+		return "34"
+	}
+	return strconv.Itoa(vendorApiLevel - 100)
+}
+
 func (c *config) VendorApiLevelFrozen() bool {
 	return c.productVariables.GetBuildFlagBool("RELEASE_BOARD_API_LEVEL_FROZEN")
 }