diff --git a/filesystem/filesystem.go b/filesystem/filesystem.go
index fbc8089..b6b4cb7 100644
--- a/filesystem/filesystem.go
+++ b/filesystem/filesystem.go
@@ -53,6 +53,12 @@
 	})
 }
 
+// Remember to add referenced files to implicits!
+var textFileProcessorRule = pctx.AndroidStaticRule("text_file_processing", blueprint.RuleParams{
+	Command:     "build/soong/scripts/text_file_processor.py $in $out",
+	CommandDeps: []string{"build/soong/scripts/text_file_processor.py"},
+})
+
 type filesystem struct {
 	android.ModuleBase
 	android.PackagingBase
@@ -107,6 +113,9 @@
 	// avbtool. Default used by avbtool is sha1.
 	Avb_hash_algorithm *string
 
+	// Whether or not to use forward-error-correction codes when signing with AVB. Defaults to true.
+	Use_fec *bool
+
 	// The index used to prevent rollback of the image. Only used if use_avb is true.
 	Rollback_index *int64
 
@@ -563,11 +572,21 @@
 		FlagWithArg("--out_system=", rootDir.String()+"/system")
 
 	propFile, toolDeps := f.buildPropFile(ctx)
+
+	// Most of the time, if build_image were to call a host tool, it accepts the path to the
+	// host tool in a field in the prop file. However, it doesn't have that option for fec, which
+	// it expects to just be on the PATH. Add fec to the PATH.
+	fec := ctx.Config().HostToolPath(ctx, "fec")
+	pathToolDirs := []string{filepath.Dir(fec.String())}
+
 	output := android.PathForModuleOut(ctx, f.installFileName())
-	builder.Command().BuiltTool("build_image").
+	builder.Command().
+		Textf("PATH=%s:$PATH", strings.Join(pathToolDirs, ":")).
+		BuiltTool("build_image").
 		Text(rootDir.String()). // input directory
 		Input(propFile).
 		Implicits(toolDeps).
+		Implicit(fec).
 		Output(output).
 		Text(rootDir.String()) // directory where to find fs_config_files|dirs
 
@@ -634,10 +653,15 @@
 		addPath("avb_avbtool", ctx.Config().HostToolPath(ctx, "avbtool"))
 		algorithm := proptools.StringDefault(f.properties.Avb_algorithm, "SHA256_RSA4096")
 		addStr("avb_algorithm", algorithm)
-		key := android.PathForModuleSrc(ctx, proptools.String(f.properties.Avb_private_key))
-		addPath("avb_key_path", key)
+		if f.properties.Avb_private_key != nil {
+			key := android.PathForModuleSrc(ctx, *f.properties.Avb_private_key)
+			addPath("avb_key_path", key)
+		}
 		addStr("partition_name", f.partitionName())
-		avb_add_hashtree_footer_args := "--do_not_generate_fec"
+		avb_add_hashtree_footer_args := ""
+		if !proptools.BoolDefault(f.properties.Use_fec, true) {
+			avb_add_hashtree_footer_args += " --do_not_generate_fec"
+		}
 		if hashAlgorithm := proptools.String(f.properties.Avb_hash_algorithm); hashAlgorithm != "" {
 			avb_add_hashtree_footer_args += " --hash_algorithm " + hashAlgorithm
 		}
@@ -648,9 +672,9 @@
 			}
 			avb_add_hashtree_footer_args += " --rollback_index " + strconv.Itoa(rollbackIndex)
 		}
-		securityPatchKey := "com.android.build." + f.partitionName() + ".security_patch"
-		securityPatchValue := ctx.Config().PlatformSecurityPatch()
-		avb_add_hashtree_footer_args += " --prop " + securityPatchKey + ":" + securityPatchValue
+		avb_add_hashtree_footer_args += fmt.Sprintf(" --prop com.android.build.%s.os_version:%s", f.partitionName(), ctx.Config().PlatformVersionLastStable())
+		avb_add_hashtree_footer_args += fmt.Sprintf(" --prop com.android.build.%s.fingerprint:{CONTENTS_OF:%s}", f.partitionName(), ctx.Config().BuildFingerprintFile(ctx))
+		avb_add_hashtree_footer_args += fmt.Sprintf(" --prop com.android.build.%s.security_patch:%s", f.partitionName(), ctx.Config().PlatformSecurityPatch())
 		addStr("avb_add_hashtree_footer_args", avb_add_hashtree_footer_args)
 		addStr("avb_salt", f.salt())
 	}
@@ -694,8 +718,15 @@
 	}
 	f.checkFsTypePropertyError(ctx, fst, fsTypeStr(fst))
 
+	propFilePreProcessing := android.PathForModuleOut(ctx, "prop_pre_processing")
+	android.WriteFileRuleVerbatim(ctx, propFilePreProcessing, propFileString.String())
 	propFile := android.PathForModuleOut(ctx, "prop")
-	android.WriteFileRuleVerbatim(ctx, propFile, propFileString.String())
+	ctx.Build(pctx, android.BuildParams{
+		Rule:     textFileProcessorRule,
+		Input:    propFilePreProcessing,
+		Output:   propFile,
+		Implicit: ctx.Config().BuildFingerprintFile(ctx),
+	})
 	return propFile, deps
 }
 
diff --git a/filesystem/filesystem_test.go b/filesystem/filesystem_test.go
index 72a5211..86496eb 100644
--- a/filesystem/filesystem_test.go
+++ b/filesystem/filesystem_test.go
@@ -593,7 +593,7 @@
 	`)
 
 	partition := result.ModuleForTests("erofs_partition", "android_common")
-	buildImageConfig := android.ContentFromFileRuleForTests(t, result.TestContext, partition.Output("prop"))
+	buildImageConfig := android.ContentFromFileRuleForTests(t, result.TestContext, partition.Output("prop_pre_processing"))
 	android.AssertStringDoesContain(t, "erofs fs type", buildImageConfig, "fs_type=erofs")
 	android.AssertStringDoesContain(t, "erofs fs type compress algorithm", buildImageConfig, "erofs_default_compressor=lz4hc,9")
 	android.AssertStringDoesContain(t, "erofs fs type compress hint", buildImageConfig, "erofs_default_compress_hints=compress_hints.txt")
@@ -609,7 +609,7 @@
 	`)
 
 	partition := result.ModuleForTests("f2fs_partition", "android_common")
-	buildImageConfig := android.ContentFromFileRuleForTests(t, result.TestContext, partition.Output("prop"))
+	buildImageConfig := android.ContentFromFileRuleForTests(t, result.TestContext, partition.Output("prop_pre_processing"))
 	android.AssertStringDoesContain(t, "f2fs fs type", buildImageConfig, "fs_type=f2fs")
 	android.AssertStringDoesContain(t, "f2fs fs type sparse", buildImageConfig, "f2fs_sparse_flag=-S")
 }