diff --git a/shaka/include/shaka/media/frames.h b/shaka/include/shaka/media/frames.h
index 2fd9bd9c..a1ae8fa0 100644
--- a/shaka/include/shaka/media/frames.h
+++ b/shaka/include/shaka/media/frames.h
@@ -16,6 +16,7 @@
 #define SHAKA_EMBEDDED_MEDIA_FRAMES_H_
 
 #include <iostream>
+#include <memory>
 #include <vector>
 
 #include "../eme/configuration.h"
@@ -217,6 +218,10 @@ class SHAKA_EXPORT BaseFrame {
    * @return The estimated size of the frame, in bytes.
    */
   virtual size_t EstimateSize() const;
+
+ private:
+  class Impl;
+  std::unique_ptr<Impl> impl_;
 };
 
 /**
@@ -264,6 +269,10 @@ class SHAKA_EXPORT EncodedFrame : public BaseFrame {
 
 
   size_t EstimateSize() const override;
+
+ private:
+  class Impl;
+  std::unique_ptr<Impl> impl_;
 };
 
 /**
@@ -317,6 +326,10 @@ class SHAKA_EXPORT DecodedFrame : public BaseFrame {
 
 
   size_t EstimateSize() const override;
+
+ private:
+  class Impl;
+  std::unique_ptr<Impl> impl_;
 };
 
 }  // namespace media
diff --git a/shaka/include/shaka/media/media_track.h b/shaka/include/shaka/media/media_track.h
index b735581d..edd8e280 100644
--- a/shaka/include/shaka/media/media_track.h
+++ b/shaka/include/shaka/media/media_track.h
@@ -104,6 +104,8 @@ class SHAKA_EXPORT MediaTrack {
   virtual void SetEnabled(bool enabled);
 
  private:
+  class Impl;
+  std::unique_ptr<Impl> impl_;
   bool enabled_;
 };
 
diff --git a/shaka/src/media/frames.cc b/shaka/src/media/frames.cc
index c1632c8e..4cbabaef 100644
--- a/shaka/src/media/frames.cc
+++ b/shaka/src/media/frames.cc
@@ -110,6 +110,8 @@ size_t GetPlaneCount(variant<PixelFormat, SampleFormat> format,
 }
 
 
+class BaseFrame::Impl {};
+
 BaseFrame::BaseFrame(std::shared_ptr<const StreamInfo> stream_info, double pts,
                      double dts, double duration, bool is_key_frame)
     : stream_info(stream_info),
@@ -120,10 +122,12 @@ BaseFrame::BaseFrame(std::shared_ptr<const StreamInfo> stream_info, double pts,
 BaseFrame::~BaseFrame() {}
 
 size_t BaseFrame::EstimateSize() const {
-  return sizeof(*this);
+  return sizeof(*this) + sizeof(Impl);
 }
 
 
+class EncodedFrame::Impl {};
+
 EncodedFrame::EncodedFrame(
     std::shared_ptr<const StreamInfo> stream, double pts, double dts,
     double duration, bool is_key_frame, const uint8_t* data, size_t data_size,
@@ -156,10 +160,15 @@ MediaStatus EncodedFrame::Decrypt(const eme::Implementation* implementation,
 }
 
 size_t EncodedFrame::EstimateSize() const {
-  return sizeof(*this) + data_size;
+  // BaseFrame::EstimateSize includes sizeof(BaseFrame) and so does
+  // sizeof(this), so we need to remove the extra.
+  return BaseFrame::EstimateSize() + sizeof(*this) - sizeof(BaseFrame) +
+         data_size + sizeof(Impl);
 }
 
 
+class DecodedFrame::Impl {};
+
 DecodedFrame::DecodedFrame(std::shared_ptr<const StreamInfo> stream, double pts,
                            double dts, double duration,
                            variant<PixelFormat, SampleFormat> format,
@@ -174,7 +183,10 @@ DecodedFrame::DecodedFrame(std::shared_ptr<const StreamInfo> stream, double pts,
 DecodedFrame::~DecodedFrame() {}
 
 size_t DecodedFrame::EstimateSize() const {
-  size_t ret = sizeof(*this);
+  // BaseFrame::EstimateSize includes sizeof(BaseFrame) and so does
+  // sizeof(this), so we need to remove the extra.
+  size_t ret = BaseFrame::EstimateSize() + sizeof(*this) - sizeof(BaseFrame) +
+               sizeof(Impl);
   for (size_t line : linesize) {
     if (holds_alternative<PixelFormat>(format))
       ret += line * stream_info->height;
diff --git a/shaka/src/media/media_track_public.cc b/shaka/src/media/media_track_public.cc
index ee5874e8..7b3167b8 100644
--- a/shaka/src/media/media_track_public.cc
+++ b/shaka/src/media/media_track_public.cc
@@ -17,6 +17,8 @@
 namespace shaka {
 namespace media {
 
+class MediaTrack::Impl {};
+
 MediaTrack::MediaTrack(MediaTrackKind kind, const std::string& label,
                        const std::string& language, const std::string& id)
     : label(label), language(language), id(id), kind(kind), enabled_(false) {}