diff --git a/src/partition/repart.c b/src/partition/repart.c
index c7791178b4..fc33a3eb62 100644
--- a/src/partition/repart.c
+++ b/src/partition/repart.c
@@ -1922,6 +1922,8 @@ static int determine_current_padding(
                 return log_error_errno(SYNTHETIC_ERRNO(EIO), "Partition has no end!");
 
         offset = fdisk_partition_get_end(p);
+        assert(offset < UINT64_MAX);
+        offset++; /* The end is one sector before the next partition or padding. */
         assert(offset < UINT64_MAX / secsz);
         offset *= secsz;
 
@@ -2108,7 +2110,7 @@ static int context_load_partition_table(Context *context) {
                         return log_error_errno(errno, "Failed to stat block device '%s': %m", context->node);
 
                 if (S_ISREG(st.st_mode) && st.st_size == 0) {
-                        /* User the fallback values if we have no better idea */
+                        /* Use the fallback values if we have no better idea */
                         context->sector_size = arg_sector_size ?: 512;
                         context->grain_size = 4096;
                         return /* from_scratch = */ true;
diff --git a/test/units/testsuite-58.sh b/test/units/testsuite-58.sh
index 6ddb96d26e..c7510dd3fc 100755
--- a/test/units/testsuite-58.sh
+++ b/test/units/testsuite-58.sh
@@ -1021,6 +1021,88 @@ EOF
     systemd-dissect -U "$imgs/mnt"
 }
 
+testcase_free_area_calculation() {
+    local defs imgs output
+
+    if ! command -v mksquashfs >/dev/null; then
+        echo "Skipping free area calculation test without squashfs."
+        return
+    fi
+
+    defs="$(mktemp --directory "/tmp/test-repart.defs.XXXXXXXXXX")"
+    imgs="$(mktemp --directory "/var/tmp/test-repart.imgs.XXXXXXXXXX")"
+    # shellcheck disable=SC2064
+    trap "rm -rf '$defs' '$imgs'" RETURN
+    chmod a+rx "$defs"
+
+    # https://github.com/systemd/systemd/issues/28225
+    echo "*** free area calculation ***"
+
+    tee "$defs/00-ESP.conf" <<EOF
+[Partition]
+Type         = esp
+Label        = ESP
+Format       = vfat
+
+SizeMinBytes = 128M
+SizeMaxBytes = 128M
+
+# Sufficient for testing
+CopyFiles    = /etc:/
+EOF
+
+    tee "$defs/10-os.conf" <<EOF
+[Partition]
+Type           = root-${architecture}
+Label          = test
+Format         = squashfs
+
+Minimize       = best
+# Sufficient for testing
+CopyFiles      = /etc/:/
+
+VerityMatchKey = os
+Verity         = data
+EOF
+
+    tee "$defs/11-os-verity.conf" <<EOF
+[Partition]
+Type           = root-${architecture}-verity
+Label          = test
+
+Minimize       = best
+
+VerityMatchKey = os
+Verity         = hash
+EOF
+
+    # Set sector size for VFAT to 512 bytes because there will not be enough FAT clusters otherwise
+    output1=$(SYSTEMD_REPART_MKFS_OPTIONS_VFAT="-S 512" systemd-repart \
+                                              --definitions="$defs" \
+                                              --seed="$seed" \
+                                              --dry-run=no \
+                                              --empty=create \
+                                              --size=auto \
+                                              --sector-size=4096 \
+                                              --defer-partitions=esp \
+                                              --json=pretty \
+                                              "$imgs/zzz")
+
+    # The second invocation
+    output2=$(SYSTEMD_REPART_MKFS_OPTIONS_VFAT="-S 512" systemd-repart \
+                                              --definitions="$defs" \
+                                              --seed="$seed" \
+                                              --dry-run=no \
+                                              --empty=allow \
+                                              --size=auto \
+                                              --sector-size=4096 \
+                                              --defer-partitions=esp \
+                                              --json=pretty \
+                                              "$imgs/zzz")
+
+    diff -u <(echo "$output1" | grep -E "(offset|raw_size|raw_padding)") <(echo "$output2" | grep -E "(offset|raw_size|raw_padding)")
+}
+
 test_sector() {
     local defs imgs output loop
     local start size ratio