diff --git a/extern/nanohttpd/core/build.gradle b/extern/nanohttpd/core/build.gradle
index 65458666e..fa98bdbea 100644
--- a/extern/nanohttpd/core/build.gradle
+++ b/extern/nanohttpd/core/build.gradle
@@ -2,6 +2,9 @@ apply plugin: 'java'
 
 version = '2.1.0'
 
+sourceCompatibility = 1.7
+targetCompatibility = 1.7
+
 jar {
     baseName = 'nanohttpd'
 }
diff --git a/extern/zipsigner/build.gradle b/extern/zipsigner/build.gradle
index 434dfe7d6..39051b869 100644
--- a/extern/zipsigner/build.gradle
+++ b/extern/zipsigner/build.gradle
@@ -4,6 +4,9 @@ repositories {
     jcenter()
 }
 
+sourceCompatibility = 1.7
+targetCompatibility = 1.7
+
 dependencies {
     compile 'com.madgag.spongycastle:pkix:1.53.0.0'
     compile 'com.madgag.spongycastle:prov:1.53.0.0'