diff --git a/webrtc/BUILD.gn b/webrtc/BUILD.gn
index 40368597b2..56d06cf129 100644
--- a/webrtc/BUILD.gn
+++ b/webrtc/BUILD.gn
@@ -154,14 +154,18 @@ config("common_config") {
   }
 
   if (is_android && !is_clang) {
-    # The Android NDK doesn"t provide optimized versions of these
-    # functions. Ensure they are disabled for all compilers.
     cflags += [
+      # The Android NDK doesn't provide optimized versions of these
+      # functions. Ensure they are disabled for all compilers.
       "-fno-builtin-cos",
       "-fno-builtin-sin",
       "-fno-builtin-cosf",
       "-fno-builtin-sinf",
     ]
+    cflags_c = [
+      # Use C99 mode instead of C89 (default).
+      "-std=c99",
+    ]
   }
 }
 
diff --git a/webrtc/build/common.gypi b/webrtc/build/common.gypi
index 5caa6cc10c..be1451d643 100644
--- a/webrtc/build/common.gypi
+++ b/webrtc/build/common.gypi
@@ -373,14 +373,18 @@
          ],
          'conditions': [
            ['clang==0', {
-             # The Android NDK doesn't provide optimized versions of these
-             # functions. Ensure they are disabled for all compilers.
              'cflags': [
+               # The Android NDK doesn't provide optimized versions of these
+               # functions. Ensure they are disabled for all compilers.
                '-fno-builtin-cos',
                '-fno-builtin-sin',
                '-fno-builtin-cosf',
                '-fno-builtin-sinf',
              ],
+             'cflags_c': [
+               # Use C99 mode instead of C89 (default).
+               '-std=c99',
+             ]
            }],
          ],
       }],
diff --git a/webrtc/modules/audio_coding/codecs/ilbc/nearest_neighbor.c b/webrtc/modules/audio_coding/codecs/ilbc/nearest_neighbor.c
index 2b58abc4f9..af0404537f 100644
--- a/webrtc/modules/audio_coding/codecs/ilbc/nearest_neighbor.c
+++ b/webrtc/modules/audio_coding/codecs/ilbc/nearest_neighbor.c
@@ -22,9 +22,8 @@ void WebRtcIlbcfix_NearestNeighbor(size_t* index,
                                    const size_t* array,
                                    size_t value,
                                    size_t arlength) {
-  size_t i;
   size_t min_diff = (size_t)-1;
-  for (i = 0; i < arlength; i++) {
+  for (size_t i = 0; i < arlength; i++) {
     const size_t diff =
         (array[i] < value) ? (value - array[i]) : (array[i] - value);
     if (diff < min_diff) {