diff --git a/java/aar.go b/java/aar.go
index 47f6e5f..a2c203f 100644
--- a/java/aar.go
+++ b/java/aar.go
@@ -499,7 +499,7 @@
 }
 
 func (a *AARImport) sdkVersion() string {
-	return String(a.properties.Sdk_version)
+	return proptools.StringDefault(a.properties.Sdk_version, defaultSdkVersion(a))
 }
 
 func (a *AARImport) minSdkVersion() string {
diff --git a/java/droiddoc.go b/java/droiddoc.go
index be1b281..18f337a 100644
--- a/java/droiddoc.go
+++ b/java/droiddoc.go
@@ -23,6 +23,7 @@
 	"strings"
 
 	"github.com/google/blueprint"
+	"github.com/google/blueprint/proptools"
 )
 
 var (
@@ -523,7 +524,7 @@
 var _ android.OutputFileProducer = (*Javadoc)(nil)
 
 func (j *Javadoc) sdkVersion() string {
-	return String(j.properties.Sdk_version)
+	return proptools.StringDefault(j.properties.Sdk_version, defaultSdkVersion(j))
 }
 
 func (j *Javadoc) minSdkVersion() string {
diff --git a/java/java.go b/java/java.go
index a2e9ab0..0378436 100644
--- a/java/java.go
+++ b/java/java.go
@@ -426,6 +426,18 @@
 	usesLibTag            = dependencyTag{name: "uses-library"}
 )
 
+func defaultSdkVersion(ctx checkVendorModuleContext) string {
+	if ctx.SocSpecific() || ctx.DeviceSpecific() {
+		return "system_current"
+	}
+	return ""
+}
+
+type checkVendorModuleContext interface {
+	SocSpecific() bool
+	DeviceSpecific() bool
+}
+
 type sdkDep struct {
 	useModule, useFiles, useDefaultLibs, invalidVersion bool
 
@@ -465,7 +477,7 @@
 }
 
 func (j *Module) sdkVersion() string {
-	return String(j.deviceProperties.Sdk_version)
+	return proptools.StringDefault(j.deviceProperties.Sdk_version, defaultSdkVersion(j))
 }
 
 func (j *Module) minSdkVersion() string {
@@ -1869,7 +1881,7 @@
 }
 
 func (j *Import) sdkVersion() string {
-	return String(j.properties.Sdk_version)
+	return proptools.StringDefault(j.properties.Sdk_version, defaultSdkVersion(j))
 }
 
 func (j *Import) minSdkVersion() string {
diff --git a/java/java_test.go b/java/java_test.go
index 22dec07..628fec3 100644
--- a/java/java_test.go
+++ b/java/java_test.go
@@ -282,6 +282,32 @@
 	}
 }
 
+func TestSdkVersion(t *testing.T) {
+	ctx := testJava(t, `
+		java_library {
+			name: "foo",
+			srcs: ["a.java"],
+			vendor: true,
+		}
+
+		java_library {
+			name: "bar",
+			srcs: ["b.java"],
+		}
+	`)
+
+	foo := ctx.ModuleForTests("foo", "android_common").Module().(*Library)
+	bar := ctx.ModuleForTests("bar", "android_common").Module().(*Library)
+
+	if foo.sdkVersion() != "system_current" {
+		t.Errorf("If sdk version of vendor module is empty, it must change to system_current.")
+	}
+
+	if bar.sdkVersion() != "" {
+		t.Errorf("If sdk version of non-vendor module is empty, it keeps empty.")
+	}
+}
+
 func TestArchSpecific(t *testing.T) {
 	ctx := testJava(t, `
 		java_library {