diff --git a/src/shared/loop-util.c b/src/shared/loop-util.c
index fd68af4160..def2fa89fb 100644
--- a/src/shared/loop-util.c
+++ b/src/shared/loop-util.c
@@ -824,7 +824,7 @@ static int resize_partition(int partition_fd, uint64_t offset, uint64_t size) {
 
         assert(S_ISBLK(st.st_mode));
 
-        xsprintf(sysfs, "/sys/dev/block/%u:%u/partition", major(st.st_rdev), minor(st.st_rdev));
+        xsprintf(sysfs, "/sys/dev/block/" DEVNUM_FORMAT_STR "/partition", DEVNUM_FORMAT_VAL(st.st_rdev));
         r = read_one_line_file(sysfs, &buffer);
         if (r == -ENOENT) /* not a partition, cannot resize */
                 return -ENOTTY;
@@ -834,7 +834,7 @@ static int resize_partition(int partition_fd, uint64_t offset, uint64_t size) {
         if (r < 0)
                 return r;
 
-        xsprintf(sysfs, "/sys/dev/block/%u:%u/start", major(st.st_rdev), minor(st.st_rdev));
+        xsprintf(sysfs, "/sys/dev/block/" DEVNUM_FORMAT_STR "/start", DEVNUM_FORMAT_VAL(st.st_rdev));
 
         buffer = mfree(buffer);
         r = read_one_line_file(sysfs, &buffer);
@@ -855,7 +855,7 @@ static int resize_partition(int partition_fd, uint64_t offset, uint64_t size) {
         if (current_size == size && current_offset == offset)
                 return 0;
 
-        xsprintf(sysfs, "/sys/dev/block/%u:%u/../dev", major(st.st_rdev), minor(st.st_rdev));
+        xsprintf(sysfs, "/sys/dev/block/" DEVNUM_FORMAT_STR "/../dev", DEVNUM_FORMAT_VAL(st.st_rdev));
 
         buffer = mfree(buffer);
         r = read_one_line_file(sysfs, &buffer);