diff --git a/payload_consumer/delta_performer.cc b/payload_consumer/delta_performer.cc
index 5ad1d46..687f903 100644
--- a/payload_consumer/delta_performer.cc
+++ b/payload_consumer/delta_performer.cc
@@ -130,6 +130,35 @@
   *err = 0;
   return fd;
 }
+
+// Discard the tail of the block device referenced by |fd|, from the offset
+// |data_size| until the end of the block device. Returns whether the data was
+// discarded.
+bool DiscardPartitionTail(FileDescriptorPtr fd, uint64_t data_size) {
+  uint64_t part_size = fd->BlockDevSize();
+  if (!part_size || part_size <= data_size)
+    return false;
+
+  const vector<int> requests = {
+      BLKSECDISCARD,
+      BLKDISCARD,
+#ifdef BLKZEROOUT
+      BLKZEROOUT,
+#endif
+  };
+  for (int request : requests) {
+    int error = 0;
+    if (fd->BlkIoctl(request, data_size, part_size - data_size, &error) &&
+        error == 0) {
+      return true;
+    }
+    LOG(WARNING) << "Error discarding the last "
+                 << (part_size - data_size) / 1024 << " KiB using ioctl("
+                 << request << ")";
+  }
+  return false;
+}
+
 }  // namespace
 
 
@@ -325,6 +354,15 @@
                << ", file " << target_path_;
     return false;
   }
+
+  LOG(INFO) << "Applying " << partition.operations().size()
+            << " operations to partition \"" << partition.partition_name()
+            << "\"";
+
+  // Discard the end of the partition, but ignore failures.
+  DiscardPartitionTail(
+      target_fd_, install_plan_->partitions[current_partition_].target_size);
+
   return true;
 }
 
diff --git a/payload_consumer/file_descriptor.cc b/payload_consumer/file_descriptor.cc
index 309c60d..8a23dea 100644
--- a/payload_consumer/file_descriptor.cc
+++ b/payload_consumer/file_descriptor.cc
@@ -24,6 +24,8 @@
 
 #include <base/posix/eintr_wrapper.h>
 
+#include "update_engine/common/utils.h"
+
 namespace chromeos_update_engine {
 
 bool EintrSafeFileDescriptor::Open(const char* path, int flags, mode_t mode) {
@@ -65,6 +67,20 @@
   return lseek64(fd_, offset, whence);
 }
 
+uint64_t EintrSafeFileDescriptor::BlockDevSize() {
+  if (fd_ < 0)
+    return 0;
+  struct stat stbuf;
+  if (fstat(fd_, &stbuf) < 0) {
+    PLOG(ERROR) << "Error stat-ing fd " << fd_;
+    return 0;
+  }
+  if (!S_ISBLK(stbuf.st_mode))
+    return 0;
+  off_t block_size = utils::BlockDevSize(fd_);
+  return block_size < 0 ? 0 : block_size;
+}
+
 bool EintrSafeFileDescriptor::BlkIoctl(int request,
                                        uint64_t start,
                                        uint64_t length,
diff --git a/payload_consumer/file_descriptor.h b/payload_consumer/file_descriptor.h
index 3c15415..7bb2974 100644
--- a/payload_consumer/file_descriptor.h
+++ b/payload_consumer/file_descriptor.h
@@ -78,6 +78,10 @@
   // may set errno accordingly.
   virtual off64_t Seek(off64_t offset, int whence) = 0;
 
+  // Return the size of the block device in bytes, or 0 if the device is not a
+  // block device or an error occurred.
+  virtual uint64_t BlockDevSize() = 0;
+
   // Runs a ioctl() on the file descriptor if supported. Returns whether
   // the operation is supported. The |request| can be one of BLKDISCARD,
   // BLKZEROOUT and BLKSECDISCARD to discard, write zeros or securely discard
@@ -119,6 +123,7 @@
   ssize_t Read(void* buf, size_t count) override;
   ssize_t Write(const void* buf, size_t count) override;
   off64_t Seek(off64_t offset, int whence) override;
+  uint64_t BlockDevSize() override;
   bool BlkIoctl(int request,
                 uint64_t start,
                 uint64_t length,
diff --git a/payload_consumer/mtd_file_descriptor.h b/payload_consumer/mtd_file_descriptor.h
index 9ac1ec1..6c945b2 100644
--- a/payload_consumer/mtd_file_descriptor.h
+++ b/payload_consumer/mtd_file_descriptor.h
@@ -40,6 +40,7 @@
   ssize_t Read(void* buf, size_t count) override;
   ssize_t Write(const void* buf, size_t count) override;
   off64_t Seek(off64_t offset, int whence) override;
+  uint64_t BlockDevSize() override { return 0; }
   bool BlkIoctl(int request,
                 uint64_t start,
                 uint64_t length,
@@ -75,6 +76,7 @@
   ssize_t Read(void* buf, size_t count) override;
   ssize_t Write(const void* buf, size_t count) override;
   off64_t Seek(off64_t offset, int whence) override;
+  uint64_t BlockDevSize() override { return 0; }
   bool BlkIoctl(int request,
                 uint64_t start,
                 uint64_t length,