diff --git a/src/bin/pg_probackup/data.cpp b/src/bin/pg_probackup/data.cpp
index 9d589ecfe..36b3d488f 100644
--- a/src/bin/pg_probackup/data.cpp
+++ b/src/bin/pg_probackup/data.cpp
@@ -114,9 +114,15 @@ uint16 pg_checksum_page(char* page, BlockNumber blkno)
      * the API of this function.
      */
     save_checksum = phdr->pd_checksum;
+    uint16 lower = phdr->pd_lower;
+    
     phdr->pd_checksum = 0;
+    phdr->pd_lower &= (COMP_ASIGNMENT - 1);
+    
     checksum = pg_checksum_block(page, BLCKSZ);
+    
     phdr->pd_checksum = save_checksum;
+    phdr->pd_lower = lower;
 
     /* Mix in the block number to detect transposed pages */
     checksum ^= blkno;
diff --git a/src/lib/page_compression/PageCompression.cpp b/src/lib/page_compression/PageCompression.cpp
index ef5be9520..9718795a3 100644
--- a/src/lib/page_compression/PageCompression.cpp
+++ b/src/lib/page_compression/PageCompression.cpp
@@ -302,7 +302,7 @@ size_t CalRealWriteSize(char *buffer)
     }
 
     /* check the assignment made during backup */
-    if ((phdr->pd_lower & COMP_ASIGNMENT) == 0) {
+    if (phdr->pd_lower & COMP_ASIGNMENT) {
         return BLCKSZ;
     }