diff --git a/talk/build/common.gypi b/talk/build/common.gypi
index edbf0f3ca..a8fcd57aa 100644
--- a/talk/build/common.gypi
+++ b/talk/build/common.gypi
@@ -29,18 +29,22 @@
 
 {
   'variables': {
-   'webrtc_root%': '<(DEPTH)/webrtc',
+    'webrtc_root%': '<(DEPTH)/webrtc',
     # TODO(ronghuawu): Chromium build will need a different libjingle_root.
     'libjingle_root%': '<(DEPTH)',
     # TODO(ronghuawu): For now, disable the Chrome plugins, which causes a
     # flood of chromium-style warnings.
     'clang_use_chrome_plugins%': 0,
     'libpeer_target_type%': 'static_library',
-    # TODO(henrike): make sure waterfall bots have $JAVA_HOME configured
-    # properly and remove the default value below. See issue 2113.
-    'java_home%': '<!(python -c "import os; print os.getenv(\'JAVA_HOME\', \'/usr/lib/jvm/java-6-sun\');")',
     # Whether or not to build the ObjectiveC PeerConnection API & tests.
-    'libjingle_objc%' : 0,
+    'libjingle_objc%': 0,
+    'conditions': [
+      ['OS=="android" or OS=="linux"', {
+        # TODO(henrike): make sure waterfall bots have $JAVA_HOME configured
+        # properly and remove the default value below. See issue 2113.
+        'java_home%': '<!(python -c "import os; dir=os.getenv(\'JAVA_HOME\', \'/usr/lib/jvm/java-6-sun\'); assert os.path.exists(os.path.join(dir, \'include/jni.h\')), \'Point \\$JAVA_HOME or the java_home gyp variable to a directory containing include/jni.h!\'; print dir")',
+      }],
+    ],
   },
   'target_defaults': {
     'include_dirs': [
diff --git a/talk/libjingle_examples.gyp b/talk/libjingle_examples.gyp
index cc252b2a9..78bfe654f 100755
--- a/talk/libjingle_examples.gyp
+++ b/talk/libjingle_examples.gyp
@@ -266,9 +266,20 @@
               # Ideally app signing would be a part of gyp.
               # Delete if/when that comes to pass.
               'postbuild_name': 'Sign AppRTCDemo',
+              'variables': {
+                'variables': {
+                  'key_id%': '<!(security find-identity -p codesigning -v | grep "iPhone Developer" | awk \'{print $2}\')',
+                },
+                'key_id%': '<(key_id)',
+                # Total HACK to give a more informative message when multiple
+                # codesigning keys are present in the default keychain.  Ideally
+                # we could pick more intelligently among the keys, but as a
+                # first cut just tell the developer to specify a key identity
+                # explicitly.
+                'ensure_single_key': '<!(python -c "assert len(\'\'\'<(key_id)\'\'\') > 0 and \'\\n\' not in \'\'\'<(key_id)\'\'\', \'key_id gyp variable needs to be set explicitly because there are multiple codesigning keys, or none!\'")',
+              },
               'action': [
-                '/usr/bin/codesign', '-v', '--force', '--sign',
-                '<!(security find-identity -p codesigning -v | grep "iPhone Developer" | awk \'{print $2}\')',
+                '/usr/bin/codesign', '-v', '--force', '--sign', '<(key_id)',
                 '${BUILT_PRODUCTS_DIR}/AppRTCDemo.app',
               ],
             },