diff --git a/modules/audio_processing/aec3/aec3_fft.cc b/modules/audio_processing/aec3/aec3_fft.cc
index 5c9a061cba..b02f3425b7 100644
--- a/modules/audio_processing/aec3/aec3_fft.cc
+++ b/modules/audio_processing/aec3/aec3_fft.cc
@@ -98,7 +98,7 @@ void Aec3Fft::ZeroPaddedFft(rtc::ArrayView<const float> x,
 }
 
 void Aec3Fft::PaddedFft(rtc::ArrayView<const float> x,
-                        rtc::ArrayView<float> x_old,
+                        rtc::ArrayView<const float> x_old,
                         Window window,
                         FftData* X) const {
   RTC_DCHECK(X);
@@ -110,7 +110,6 @@ void Aec3Fft::PaddedFft(rtc::ArrayView<const float> x,
     case Window::kRectangular:
       std::copy(x_old.begin(), x_old.end(), fft.begin());
       std::copy(x.begin(), x.end(), fft.begin() + x_old.size());
-      std::copy(x.begin(), x.end(), x_old.begin());
       break;
     case Window::kHanning:
       RTC_NOTREACHED();
diff --git a/modules/audio_processing/aec3/aec3_fft.h b/modules/audio_processing/aec3/aec3_fft.h
index f730284745..b70022255d 100644
--- a/modules/audio_processing/aec3/aec3_fft.h
+++ b/modules/audio_processing/aec3/aec3_fft.h
@@ -51,14 +51,14 @@ class Aec3Fft {
   // Concatenates the kFftLengthBy2 values long x and x_old before computing the
   // Fft. After that, x is copied to x_old.
   void PaddedFft(rtc::ArrayView<const float> x,
-                 rtc::ArrayView<float> x_old,
+                 rtc::ArrayView<const float> x_old,
                  FftData* X) const {
     PaddedFft(x, x_old, Window::kRectangular, X);
   }
 
   // Padded Fft using a time-domain window.
   void PaddedFft(rtc::ArrayView<const float> x,
-                 rtc::ArrayView<float> x_old,
+                 rtc::ArrayView<const float> x_old,
                  Window window,
                  FftData* X) const;
 
diff --git a/modules/audio_processing/aec3/aec3_fft_unittest.cc b/modules/audio_processing/aec3/aec3_fft_unittest.cc
index 87fe7a8fbb..82d6e766cc 100644
--- a/modules/audio_processing/aec3/aec3_fft_unittest.cc
+++ b/modules/audio_processing/aec3/aec3_fft_unittest.cc
@@ -199,6 +199,7 @@ TEST(Aec3Fft, PaddedFft) {
     std::for_each(x_ref.begin(), x_ref.end(), [](float& a) { a *= 64.f; });
 
     fft.PaddedFft(x_in, x_old, &X);
+    std::copy(x_in.begin(), x_in.end(), x_old.begin());
     fft.Ifft(X, &x_out);
 
     for (size_t j = 0; j < x_out.size(); ++j) {