diff --git a/engine.c b/engine.c
index 329f13a..afaae1f 100644
--- a/engine.c
+++ b/engine.c
@@ -117,16 +117,25 @@ is_cfm_file_path(const char *filepath) {
 off_t
 get_cfs_relation_file_decompressed_size(RelFileNodeBackend rnode, const char *fullpath, ForkNumber forknum) {
 	File     fd;
-	int      compressor;
 	off_t    size;
 
+#if PG_VERSION_NUM >= 120000
+	int      compressor;
 	compressor = md_get_compressor_internal(nodeOf(rnode), rnode.backend, forknum);
 	fd = PathNameOpenFile(fullpath, O_RDWR | PG_BINARY, compressor);
+#else
+	fd = PathNameOpenFile(fullpath, O_RDWR | PG_BINARY | PG_COMPRESSION);
+#endif
 
 	if(fd < 0)
 		return (off_t)-1;
 
+#if PG_VERSION_NUM >= 120000
 	size = FileSize(fd);
+#else
+	size = FileSeek(fd, 0, SEEK_END);
+#endif
+
 	FileClose(fd);
 
 	return size;
diff --git a/engine.h b/engine.h
index 3ba868c..56777fc 100644
--- a/engine.h
+++ b/engine.h
@@ -45,7 +45,7 @@
 #define PTRACK_MAGIC_SIZE 4
 
 /* CFS support macro */
-#if defined(PGPRO_EE) && PG_VERSION_NUM >= 120000
+#if defined(PGPRO_EE) && PG_VERSION_NUM >= 110000
 #define CFS_SUPPORT 1
 #endif