diff --git a/filesystem/bootimg.go b/filesystem/bootimg.go
index fc973a4..33beb37 100644
--- a/filesystem/bootimg.go
+++ b/filesystem/bootimg.go
@@ -145,12 +145,10 @@
 	}
 
 	dtbName := proptools.String(b.properties.Dtb_prebuilt)
-	if dtbName == "" {
-		ctx.PropertyErrorf("dtb_prebuilt", "must be set")
-		return output
+	if dtbName != "" {
+		dtb := android.PathForModuleSrc(ctx, dtbName)
+		cmd.FlagWithInput("--dtb ", dtb)
 	}
-	dtb := android.PathForModuleSrc(ctx, dtbName)
-	cmd.FlagWithInput("--dtb ", dtb)
 
 	cmdline := strings.Join(b.properties.Cmdline, " ")
 	if cmdline != "" {
@@ -178,20 +176,18 @@
 	cmd.FlagWithArg("--header_version ", headerVersion)
 
 	ramdiskName := proptools.String(b.properties.Ramdisk_module)
-	if ramdiskName == "" {
-		ctx.PropertyErrorf("ramdisk_module", "must be set")
-		return output
-	}
-	ramdisk := ctx.GetDirectDepWithTag(ramdiskName, bootimgRamdiskDep)
-	if filesystem, ok := ramdisk.(*filesystem); ok {
-		flag := "--ramdisk "
-		if vendor {
-			flag = "--vendor_ramdisk "
+	if ramdiskName != "" {
+		ramdisk := ctx.GetDirectDepWithTag(ramdiskName, bootimgRamdiskDep)
+		if filesystem, ok := ramdisk.(*filesystem); ok {
+			flag := "--ramdisk "
+			if vendor {
+				flag = "--vendor_ramdisk "
+			}
+			cmd.FlagWithInput(flag, filesystem.OutputPath())
+		} else {
+			ctx.PropertyErrorf("ramdisk", "%q is not android_filesystem module", ramdisk.Name())
+			return output
 		}
-		cmd.FlagWithInput(flag, filesystem.OutputPath())
-	} else {
-		ctx.PropertyErrorf("ramdisk", "%q is not android_filesystem module", ramdisk.Name())
-		return output
 	}
 
 	bootconfig := proptools.String(b.properties.Bootconfig)