diff --git a/webrtc/modules/audio_processing/BUILD.gn b/webrtc/modules/audio_processing/BUILD.gn
index 006d3a74cd..a3434836d8 100644
--- a/webrtc/modules/audio_processing/BUILD.gn
+++ b/webrtc/modules/audio_processing/BUILD.gn
@@ -25,7 +25,7 @@ source_set("audio_processing") {
     "aec/aec_core.cc",
     "aec/aec_core.h",
     "aec/aec_core_internal.h",
-    "aec/aec_rdft.c",
+    "aec/aec_rdft.cc",
     "aec/aec_rdft.h",
     "aec/aec_resampler.cc",
     "aec/aec_resampler.h",
@@ -200,7 +200,7 @@ source_set("audio_processing") {
     if (mips_float_abi == "hard") {
       sources += [
         "aec/aec_core_mips.cc",
-        "aec/aec_rdft_mips.c",
+        "aec/aec_rdft_mips.cc",
       ]
     }
   } else {
@@ -241,7 +241,7 @@ if (current_cpu == "x86" || current_cpu == "x64") {
   source_set("audio_processing_sse2") {
     sources = [
       "aec/aec_core_sse2.cc",
-      "aec/aec_rdft_sse2.c",
+      "aec/aec_rdft_sse2.cc",
     ]
 
     if (is_posix) {
@@ -257,7 +257,7 @@ if (rtc_build_with_neon) {
   source_set("audio_processing_neon") {
     sources = [
       "aec/aec_core_neon.cc",
-      "aec/aec_rdft_neon.c",
+      "aec/aec_rdft_neon.cc",
       "aecm/aecm_core_neon.cc",
       "ns/nsx_core_neon.c",
     ]
diff --git a/webrtc/modules/audio_processing/aec/aec_core.cc b/webrtc/modules/audio_processing/aec/aec_core.cc
index 27a897a352..4b5abedd5a 100644
--- a/webrtc/modules/audio_processing/aec/aec_core.cc
+++ b/webrtc/modules/audio_processing/aec/aec_core.cc
@@ -31,9 +31,7 @@ extern "C" {
 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
 #include "webrtc/modules/audio_processing/aec/aec_common.h"
 #include "webrtc/modules/audio_processing/aec/aec_core_internal.h"
-extern "C" {
 #include "webrtc/modules/audio_processing/aec/aec_rdft.h"
-}
 #include "webrtc/modules/audio_processing/logging/aec_logging.h"
 #include "webrtc/modules/audio_processing/utility/delay_estimator_wrapper.h"
 #include "webrtc/system_wrappers/include/cpu_features_wrapper.h"
diff --git a/webrtc/modules/audio_processing/aec/aec_core_mips.cc b/webrtc/modules/audio_processing/aec/aec_core_mips.cc
index 44224d89a5..4699e35baf 100644
--- a/webrtc/modules/audio_processing/aec/aec_core_mips.cc
+++ b/webrtc/modules/audio_processing/aec/aec_core_mips.cc
@@ -20,9 +20,7 @@ extern "C" {
 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
 }
 #include "webrtc/modules/audio_processing/aec/aec_core_internal.h"
-extern "C" {
 #include "webrtc/modules/audio_processing/aec/aec_rdft.h"
-}
 
 namespace webrtc {
 
diff --git a/webrtc/modules/audio_processing/aec/aec_core_neon.cc b/webrtc/modules/audio_processing/aec/aec_core_neon.cc
index baff9bed0e..69e8d52c91 100644
--- a/webrtc/modules/audio_processing/aec/aec_core_neon.cc
+++ b/webrtc/modules/audio_processing/aec/aec_core_neon.cc
@@ -23,9 +23,7 @@ extern "C" {
 }
 #include "webrtc/modules/audio_processing/aec/aec_common.h"
 #include "webrtc/modules/audio_processing/aec/aec_core_internal.h"
-extern "C" {
 #include "webrtc/modules/audio_processing/aec/aec_rdft.h"
-}
 
 namespace webrtc {
 
diff --git a/webrtc/modules/audio_processing/aec/aec_core_sse2.cc b/webrtc/modules/audio_processing/aec/aec_core_sse2.cc
index e236a38301..254dbf10e3 100644
--- a/webrtc/modules/audio_processing/aec/aec_core_sse2.cc
+++ b/webrtc/modules/audio_processing/aec/aec_core_sse2.cc
@@ -21,9 +21,7 @@ extern "C" {
 }
 #include "webrtc/modules/audio_processing/aec/aec_common.h"
 #include "webrtc/modules/audio_processing/aec/aec_core_internal.h"
-extern "C" {
 #include "webrtc/modules/audio_processing/aec/aec_rdft.h"
-}
 
 namespace webrtc {
 
diff --git a/webrtc/modules/audio_processing/aec/aec_rdft.c b/webrtc/modules/audio_processing/aec/aec_rdft.cc
similarity index 100%
rename from webrtc/modules/audio_processing/aec/aec_rdft.c
rename to webrtc/modules/audio_processing/aec/aec_rdft.cc
diff --git a/webrtc/modules/audio_processing/aec/aec_rdft_mips.c b/webrtc/modules/audio_processing/aec/aec_rdft_mips.cc
similarity index 100%
rename from webrtc/modules/audio_processing/aec/aec_rdft_mips.c
rename to webrtc/modules/audio_processing/aec/aec_rdft_mips.cc
diff --git a/webrtc/modules/audio_processing/aec/aec_rdft_neon.c b/webrtc/modules/audio_processing/aec/aec_rdft_neon.cc
similarity index 100%
rename from webrtc/modules/audio_processing/aec/aec_rdft_neon.c
rename to webrtc/modules/audio_processing/aec/aec_rdft_neon.cc
diff --git a/webrtc/modules/audio_processing/aec/aec_rdft_sse2.c b/webrtc/modules/audio_processing/aec/aec_rdft_sse2.cc
similarity index 100%
rename from webrtc/modules/audio_processing/aec/aec_rdft_sse2.c
rename to webrtc/modules/audio_processing/aec/aec_rdft_sse2.cc
diff --git a/webrtc/modules/audio_processing/audio_processing.gypi b/webrtc/modules/audio_processing/audio_processing.gypi
index 45b3aa33e5..fd41eea48c 100644
--- a/webrtc/modules/audio_processing/audio_processing.gypi
+++ b/webrtc/modules/audio_processing/audio_processing.gypi
@@ -35,7 +35,7 @@
         'aec/aec_core.cc',
         'aec/aec_core.h',
         'aec/aec_core_internal.h',
-        'aec/aec_rdft.c',
+        'aec/aec_rdft.cc',
         'aec/aec_rdft.h',
         'aec/aec_resampler.cc',
         'aec/aec_resampler.h',
@@ -207,7 +207,7 @@
             ['mips_float_abi=="hard"', {
               'sources': [
                 'aec/aec_core_mips.cc',
-                'aec/aec_rdft_mips.c',
+                'aec/aec_rdft_mips.cc',
               ],
             }],
           ],
@@ -246,7 +246,7 @@
           'type': 'static_library',
           'sources': [
             'aec/aec_core_sse2.cc',
-            'aec/aec_rdft_sse2.c',
+            'aec/aec_rdft_sse2.cc',
           ],
           'conditions': [
             ['os_posix==1', {
@@ -269,7 +269,7 @@
         ],
         'sources': [
           'aec/aec_core_neon.cc',
-          'aec/aec_rdft_neon.c',
+          'aec/aec_rdft_neon.cc',
           'aecm/aecm_core_neon.cc',
           'ns/nsx_core_neon.c',
         ],