diff --git a/libwvdrmengine/cdm/core/src/crypto_session.cpp b/libwvdrmengine/cdm/core/src/crypto_session.cpp
index 939af6dd..f7f2b9e5 100644
--- a/libwvdrmengine/cdm/core/src/crypto_session.cpp
+++ b/libwvdrmengine/cdm/core/src/crypto_session.cpp
@@ -161,7 +161,6 @@ void AdvanceDestBuffer(OEMCrypto_DestBufferDesc* dest_buffer, size_t bytes) {
   switch (dest_buffer->type) {
     case OEMCrypto_BufferType_Clear:
       dest_buffer->buffer.clear.clear_buffer += bytes;
-      dest_buffer->buffer.clear.clear_buffer_length -= bytes;
       return;
 
     case OEMCrypto_BufferType_Secure:
@@ -3254,6 +3253,11 @@ OEMCryptoResult CryptoSession::DecryptSample(
         }
 
         fake_sample.buffers.input_data_length = length;
+        if (fake_sample.buffers.output_descriptor.type ==
+            OEMCrypto_BufferType_Clear) {
+          fake_sample.buffers.output_descriptor.buffer.clear
+              .clear_buffer_length = length;
+        }
         fake_sample.subsamples = &clear_subsample;
         fake_sample.subsamples_length = 1;
 
@@ -3281,6 +3285,11 @@ OEMCryptoResult CryptoSession::DecryptSample(
         }
 
         fake_sample.buffers.input_data_length = length;
+        if (fake_sample.buffers.output_descriptor.type ==
+            OEMCrypto_BufferType_Clear) {
+          fake_sample.buffers.output_descriptor.buffer.clear
+              .clear_buffer_length = length;
+        }
         fake_sample.subsamples = &encrypted_subsample;
         fake_sample.subsamples_length = 1;
 
@@ -3373,6 +3382,10 @@ OEMCryptoResult CryptoSession::LegacyCopyBufferInChunks(
     // Calculate the size of the next chunk.
     const size_t chunk_size = std::min(remaining_input_data, max_chunk_size);
 
+    if (output_descriptor.type == OEMCrypto_BufferType_Clear) {
+      output_descriptor.buffer.clear.clear_buffer_length = chunk_size;
+    }
+
     // Re-add "last subsample" flag if this is the last subsample.
     if (chunk_size == remaining_input_data) {
       subsample_flags |= OEMCrypto_LastSubsample;
@@ -3420,6 +3433,11 @@ OEMCryptoResult CryptoSession::LegacyDecryptInChunks(
     // Calculate the size of the next chunk.
     const size_t chunk_size = std::min(remaining_input_data, max_chunk_size);
     fake_sample.buffers.input_data_length = chunk_size;
+    if (fake_sample.buffers.output_descriptor.type ==
+        OEMCrypto_BufferType_Clear) {
+      fake_sample.buffers.output_descriptor.buffer.clear.clear_buffer_length =
+          chunk_size;
+    }
     if (is_protected) {
       fake_subsample.num_bytes_encrypted = chunk_size;
     } else {
diff --git a/libwvdrmengine/oemcrypto/test/oec_decrypt_fallback_chain.cpp b/libwvdrmengine/oemcrypto/test/oec_decrypt_fallback_chain.cpp
index 6cb7aac0..fe303fc6 100644
--- a/libwvdrmengine/oemcrypto/test/oec_decrypt_fallback_chain.cpp
+++ b/libwvdrmengine/oemcrypto/test/oec_decrypt_fallback_chain.cpp
@@ -17,7 +17,6 @@ void advance_dest_buffer(OEMCrypto_DestBufferDesc* dest_buffer, size_t bytes) {
   switch (dest_buffer->type) {
     case OEMCrypto_BufferType_Clear:
       dest_buffer->buffer.clear.clear_buffer += bytes;
-      dest_buffer->buffer.clear.clear_buffer_length -= bytes;
       break;
 
     case OEMCrypto_BufferType_Secure:
@@ -99,6 +98,11 @@ OEMCryptoResult DecryptFallbackChain::DecryptSample(
     const size_t length =
         subsample.num_bytes_clear + subsample.num_bytes_encrypted;
     fake_sample.buffers.input_data_length = length;
+    if (fake_sample.buffers.output_descriptor.type ==
+        OEMCrypto_BufferType_Clear) {
+      fake_sample.buffers.output_descriptor.buffer.clear.clear_buffer_length =
+          length;
+    }
     fake_sample.subsamples = &subsample;
     fake_sample.subsamples_length = 1;
 
@@ -144,6 +148,11 @@ OEMCryptoResult DecryptFallbackChain::DecryptSubsample(
 
   if (subsample.num_bytes_clear > 0) {
     fake_sample.buffers.input_data_length = subsample.num_bytes_clear;
+    if (fake_sample.buffers.output_descriptor.type ==
+        OEMCrypto_BufferType_Clear) {
+      fake_sample.buffers.output_descriptor.buffer.clear.clear_buffer_length =
+          subsample.num_bytes_clear;
+    }
     fake_subsample.num_bytes_clear = subsample.num_bytes_clear;
     fake_subsample.num_bytes_encrypted = 0;
     fake_subsample.block_offset = 0;
@@ -167,6 +176,11 @@ OEMCryptoResult DecryptFallbackChain::DecryptSubsample(
 
   if (subsample.num_bytes_encrypted > 0) {
     fake_sample.buffers.input_data_length = subsample.num_bytes_encrypted;
+    if (fake_sample.buffers.output_descriptor.type ==
+        OEMCrypto_BufferType_Clear) {
+      fake_sample.buffers.output_descriptor.buffer.clear.clear_buffer_length =
+          subsample.num_bytes_encrypted;
+    }
     fake_subsample.num_bytes_clear = 0;
     fake_subsample.num_bytes_encrypted = subsample.num_bytes_encrypted;
     fake_subsample.block_offset = subsample.block_offset;