diff --git a/lfs.c b/lfs.c
index fbf214ab..257abd21 100644
--- a/lfs.c
+++ b/lfs.c
@@ -2458,6 +2458,9 @@ static int lfsr_rbyd_lookupnext(lfs_t *lfs, const lfsr_rbyd_t *rbyd,
 
         // found an alt?
         if (lfsr_tag_isalt(alt)) {
+            lfs_size_t branch_ = branch + d;
+
+            // take alt?
             if (lfsr_tag_follow(
                     alt, weight,
                     lower_rid, upper_rid,
@@ -2465,19 +2468,16 @@ static int lfsr_rbyd_lookupnext(lfs_t *lfs, const lfsr_rbyd_t *rbyd,
                 lfsr_tag_flip(
                         &alt, &weight,
                         lower_rid, upper_rid);
-                lfsr_tag_trim(
-                        alt, weight,
-                        &lower_rid, &upper_rid,
-                        NULL, NULL);
-                branch = branch - jump;
-            } else {
-                lfsr_tag_trim(
-                        alt, weight,
-                        &lower_rid, &upper_rid,
-                        NULL, NULL);
-                branch = branch + d;
+                branch_ = branch - jump;
             }
 
+            lfsr_tag_trim(
+                    alt, weight,
+                    &lower_rid, &upper_rid,
+                    NULL, NULL);
+            LFS_ASSERT(branch_ != branch);
+            branch = branch_;
+
         // found end of tree?
         } else {
             // update the tag rid
@@ -2683,7 +2683,9 @@ static int lfsr_p_flush(lfs_t *lfs, lfsr_rbyd_t *rbyd,
             // change to a relative jump at the last minute
             lfsr_tag_t alt = p[3-1-i].alt;
             lfsr_rid_t weight = p[3-1-i].weight;
-            lfs_size_t jump = rbyd->eoff - p[3-1-i].jump;
+            lfs_size_t jump = (p[3-1-i].jump)
+                    ? rbyd->eoff - p[3-1-i].jump
+                    : 0;
 
             int err = lfsr_rbyd_appendtag(lfs, rbyd, alt, weight, jump);
             if (err) {
@@ -3196,6 +3198,7 @@ trunk:;
             }
 
             // continue to next alt
+            LFS_ASSERT(branch_ != branch);
             branch = branch_;
             continue;
 
diff --git a/scripts/dbgbtree.py b/scripts/dbgbtree.py
index 2ee3b909..23791ddf 100755
--- a/scripts/dbgbtree.py
+++ b/scripts/dbgbtree.py
@@ -239,8 +239,8 @@ def tagrepr(tag, w=None, size=None, off=None):
             ' 0x%x' % (tag & 0x0fff) if tag & 0x0fff != 0 else '',
             ' w%d' % w if w is not None else '',
             ' 0x%x' % (0xffffffff & (off-size))
-                if size is not None and off is not None
-                else ' -%d' % size if size is not None
+                if size and off is not None
+                else ' -%d' % size if size
                 else '')
     else:
         return '0x%04x%s%s' % (
diff --git a/scripts/dbglfs.py b/scripts/dbglfs.py
index 4fc6bf6f..8f651016 100755
--- a/scripts/dbglfs.py
+++ b/scripts/dbglfs.py
@@ -270,8 +270,8 @@ def tagrepr(tag, w=None, size=None, off=None):
             ' 0x%x' % (tag & 0x0fff) if tag & 0x0fff != 0 else '',
             ' w%d' % w if w is not None else '',
             ' 0x%x' % (0xffffffff & (off-size))
-                if size is not None and off is not None
-                else ' -%d' % size if size is not None
+                if size and off is not None
+                else ' -%d' % size if size
                 else '')
     else:
         return '0x%04x%s%s' % (
diff --git a/scripts/dbgmtree.py b/scripts/dbgmtree.py
index 589288ac..062632e6 100755
--- a/scripts/dbgmtree.py
+++ b/scripts/dbgmtree.py
@@ -254,8 +254,8 @@ def tagrepr(tag, w=None, size=None, off=None):
             ' 0x%x' % (tag & 0x0fff) if tag & 0x0fff != 0 else '',
             ' w%d' % w if w is not None else '',
             ' 0x%x' % (0xffffffff & (off-size))
-                if size is not None and off is not None
-                else ' -%d' % size if size is not None
+                if size and off is not None
+                else ' -%d' % size if size
                 else '')
     else:
         return '0x%04x%s%s' % (
diff --git a/scripts/dbgrbyd.py b/scripts/dbgrbyd.py
index eb858ff2..cc7a8046 100755
--- a/scripts/dbgrbyd.py
+++ b/scripts/dbgrbyd.py
@@ -241,8 +241,8 @@ def tagrepr(tag, w=None, size=None, off=None):
             ' 0x%x' % (tag & 0x0fff) if tag & 0x0fff != 0 else '',
             ' w%d' % w if w is not None else '',
             ' 0x%x' % (0xffffffff & (off-size))
-                if size is not None and off is not None
-                else ' -%d' % size if size is not None
+                if size and off is not None
+                else ' -%d' % size if size
                 else '')
     else:
         return '0x%04x%s%s' % (
@@ -267,8 +267,7 @@ def dbg_log(data, block_size, rev, eoff, weight, *,
             if not tag & TAG_ALT:
                 j_ += size
 
-            # skip alt-nevers
-            if tag & TAG_ALT and tag & ~TAG_R != TAG_ALT:
+            if tag & TAG_ALT and size:
                 # figure out which alt color
                 if tag & TAG_R:
                     _, ntag, _, _, _ = fromtag(data[j_:])
diff --git a/scripts/dbgtag.py b/scripts/dbgtag.py
index cb870bc1..03076500 100755
--- a/scripts/dbgtag.py
+++ b/scripts/dbgtag.py
@@ -199,8 +199,8 @@ def tagrepr(tag, w=None, size=None, off=None):
             ' 0x%x' % (tag & 0x0fff) if tag & 0x0fff != 0 else '',
             ' w%d' % w if w is not None else '',
             ' 0x%x' % (0xffffffff & (off-size))
-                if size is not None and off is not None
-                else ' -%d' % size if size is not None
+                if size and off is not None
+                else ' -%d' % size if size
                 else '')
     else:
         return '0x%04x%s%s' % (