diff --git a/payload_consumer/partition_writer_unittest.cc b/payload_consumer/partition_writer_unittest.cc
index 32324b6..ef2690f 100644
--- a/payload_consumer/partition_writer_unittest.cc
+++ b/payload_consumer/partition_writer_unittest.cc
@@ -128,7 +128,7 @@
   PartitionWriter writer_{
       partition_update_, install_part_, &dynamic_control_, kBlockSize, false};
 };
-// Test that the error-corrected file descriptor is used to read a partition
+// Test that the plain file descriptor is used to read a partition
 // when no hash is available for SOURCE_COPY but it falls back to the normal
 // file descriptor when the size of the error corrected one is too small.
 TEST_F(PartitionWriterTest, ErrorCorrectionSourceCopyWhenNoHashFallbackTest) {
@@ -153,13 +153,8 @@
   ASSERT_NO_FATAL_FAILURE();
   ASSERT_EQ(output_data, expected_data);
 
-  // Verify that the fake_fec was attempted to be used. Since the file
-  // descriptor is shorter it can actually do more than one read to realize it
-  // reached the EOF.
-  ASSERT_LE(1U, fake_fec->GetReadOps().size());
-  // This fallback doesn't count as an error-corrected operation since the
-  // operation hash was not available.
-  ASSERT_EQ(0U, GetSourceEccRecoveredFailures());
+  // Verify that the fake_fec was not used
+  ASSERT_LE(0U, fake_fec->GetReadOps().size());
 }
 
 // Test that the error-corrected file descriptor is used to read the partition
diff --git a/payload_consumer/verified_source_fd.cc b/payload_consumer/verified_source_fd.cc
index addf534..131f2fb 100644
--- a/payload_consumer/verified_source_fd.cc
+++ b/payload_consumer/verified_source_fd.cc
@@ -19,7 +19,6 @@
 #include <sys/stat.h>
 
 #include <memory>
-#include <utility>
 #include <vector>
 
 #include <base/strings/string_number_conversions.h>
@@ -90,6 +89,16 @@
     *error = ErrorCode::kSuccess;
   }
   if (!operation.has_src_sha256_hash()) {
+    if (operation.type() == InstallOperation::SOURCE_COPY) {
+      // delta_generator always adds SHA256 hash for source data. If hash is
+      // missing, the only possibility is we are doing a partial update, and
+      // currently processing a partition that's not in the payload. Data on
+      // this partition would be copied to the new slot as is. So, if the
+      // current partition boots fine(either no corruption, or with FEC), the
+      // new partition would boot fine as well. Hence, just return |source_fd_|
+      // to save time.
+      return source_fd_;
+    }
     // When the operation doesn't include a source hash, we attempt the error
     // corrected device first since we can't verify the block in the raw device
     // at this point, but we first need to make sure all extents are readable