diff --git a/lib/compatibility/2.4.nom b/lib/compatibility/2.4.nom
index 480257a..eca5d73 100644
--- a/lib/compatibility/2.4.nom
+++ b/lib/compatibility/2.4.nom
@@ -15,7 +15,7 @@ upgrade $tree to "2.4" as:
             $conditions = []
             $new_lines = []
             $body =
-                ($tree.2 upgraded) if ($tree.2 is "Block" syntax tree) else [$tree.2 upgraded]
+                $tree.2 if ($tree.2 is "Block" syntax tree) else [$tree.2]
             
             for $line in $body:
                 when:
@@ -29,7 +29,7 @@ upgrade $tree to "2.4" as:
                             $new_lines, add $line
                     
                     ($line.stub == "* else"):
-                        $new_lines, add (else \$line.3)
+                        $new_lines, add \(else \$line.3)
                     
                     else:
                         $conditions, add $line.2
@@ -49,7 +49,7 @@ upgrade $tree to "2.4" as:
             $values = []
             $new_lines = []
             $body =
-                ($tree.5 upgraded) if ($tree.5 is "Block" syntax tree) else [$tree.5 upgraded]
+                $tree.5 if ($tree.5 is "Block" syntax tree) else [$tree.5]
             
             for $line in $body:
                 when:
@@ -63,7 +63,7 @@ upgrade $tree to "2.4" as:
                             $new_lines, add $line
                     
                     ($line.stub == "* else"):
-                        $new_lines, add (else \$line.3)
+                        $new_lines, add \(else \$line.3)
                     
                     else:
                         $values, add $line.2
@@ -77,6 +77,6 @@ upgrade $tree to "2.4" as:
             
             return
                 \(
-                    if \($tree.2 upgraded) is
+                    if \($tree.2) is
                         \("Block" tree from $tree.5.source with (unpack $new_lines))
-                )
\ No newline at end of file
+                )
diff --git a/lib/compatibility/2.nom b/lib/compatibility/2.nom
index 69f2d41..17ead58 100644
--- a/lib/compatibility/2.nom
+++ b/lib/compatibility/2.nom
@@ -9,13 +9,13 @@ use "compatibility/compatibility"
 upgrade $tree to "2" as:
     unless ($tree is "Action" syntax tree): return
     if ($tree.stub == "if 1 2 else"):
-        $true_body = ($tree.3 upgraded)
+        $true_body = $tree.3
         unless ($true_body is "Block" syntax tree):
             $true_body = ("Block" tree with $true_body)
-        $false_body = ($tree.5 upgraded)
+        $false_body = $tree.5
         unless ($false_body is "Block" syntax tree):
             $false_body = (=lua "Block(\$false_body.source, \$false_body)")
-        return \(if \($tree.2 upgraded) \$true_body else \$false_body)
+        return \(if \($tree.2) \$true_body else \$false_body)
     
     $need_blocks = [
         "if", "unless", "for 1 in", "for 1 = 2 in", "repeat while 1", "repeat 1 times"
@@ -26,8 +26,8 @@ upgrade $tree to "2" as:
     
     for $n in $need_blocks:
         if ($tree.stub == $n):
-            $bits = [: for $ in $tree: add (($ upgraded) if ($ is syntax tree) else $)]
+            $bits = [: for $ in $tree: add ($ if ($ is syntax tree) else $)]
             unless (($bits, last) is "Block" syntax tree):
                 $body = ($bits, last)
                 $bits.(#$bits) = (=lua "SyntaxTree{type='Block', source=\$body.source, \$body}")
-            return (=lua "SyntaxTree{type='Action', source=\$tree.source, unpack(\$bits)}")
\ No newline at end of file
+            return (=lua "SyntaxTree{type='Action', source=\$tree.source, unpack(\$bits)}")
diff --git a/lib/compatibility/4.11.nom b/lib/compatibility/4.11.nom
index d5a158b..e263c1e 100644
--- a/lib/compatibility/4.11.nom
+++ b/lib/compatibility/4.11.nom
@@ -9,7 +9,7 @@ use "compatibility/compatibility"
 
 ### Overhaul of function literals:
 upgrade action "call 1 with" to "4.11" via
-    for ($tree $end_version):
+    for $tree:
         $tree2 = {.type = "Action", .source = $tree.source, .1 = $tree.2}
         for ($i = $arg) in $tree.4:
             $tree2.($i + 1) = $arg
@@ -18,7 +18,7 @@ upgrade action ->$yield_value to "4.11" as (yield $yield_value)
 
 ### Replace set {$x:1, $y:2} with [$x, $y] = [1, 2]
 upgrade action "set" to "4.11" via
-    for ($tree $end_version):
+    for $tree:
         [$lhs, $rhs] = [\[], \[]]
         $lhs.source = $tree.2.source
         $rhs.source = $tree.2.source
@@ -95,4 +95,4 @@ upgrade action [
 upgrade action [
     unless none of $items $body else $else
     unless none of $items then $body else $else
-] to "4.11" as (if (any of $items) $body else $else)
\ No newline at end of file
+] to "4.11" as (if (any of $items) $body else $else)
diff --git a/lib/compatibility/4.8.10.nom b/lib/compatibility/4.8.10.nom
index 5723b0d..e278efd 100644
--- a/lib/compatibility/4.8.10.nom
+++ b/lib/compatibility/4.8.10.nom
@@ -6,7 +6,7 @@ use "compatibility/compatibility"
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 upgrade action "local action" to "4.8.10" via
-    for ($tree $end_version):
+    for $tree:
         $spec = $tree.3
         $body = $tree.4
         if $spec.type is:
@@ -20,7 +20,7 @@ upgrade action "local action" to "4.8.10" via
                 return \(\$spec means \$body)
 
 upgrade action "action" to "4.8.10" via
-    for ($tree $end_version):
+    for $tree:
         $spec = $tree.2
         $body = $tree.3
         if $body:
@@ -37,7 +37,7 @@ upgrade action "action" to "4.8.10" via
             return \((\$spec)'s meaning)
 
 upgrade action "compile 1 to" to "4.8.10" via
-    for ($tree $end_version):
+    for $tree:
         $spec = $tree.2
         $body = $tree.4
         if $spec.type is:
@@ -51,7 +51,7 @@ upgrade action "compile 1 to" to "4.8.10" via
                 return \(\$spec compiles to \$body)
 
 upgrade action "parse 1 as" to "4.8.10" via
-    for ($tree $end_version):
+    for $tree:
         $spec = $tree.2
         $body = $tree.4
         if $spec.type is:
@@ -65,4 +65,4 @@ upgrade action "parse 1 as" to "4.8.10" via
                 return \(\$spec parse as \$body)
 
 upgrade action (compile as $) to "4.8.10" as (what $ compiles to)
-upgrade action (remove action $) to "4.8.10" as (($'s meaning) = (nil))
\ No newline at end of file
+upgrade action (remove action $) to "4.8.10" as (($'s meaning) = (nil))
diff --git a/lib/compatibility/4.9.nom b/lib/compatibility/4.9.nom
index 0ec8bc8..3e6aaee 100644
--- a/lib/compatibility/4.9.nom
+++ b/lib/compatibility/4.9.nom
@@ -6,7 +6,7 @@ use "compatibility/compatibility"
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 upgrade action "if" to "4.9" via
-    for ($tree $end_version):
+    for $tree:
         if (#$tree > 2):
             return $tree
-        return \(when \$tree.2)
\ No newline at end of file
+        return \(when \$tree.2)
diff --git a/lib/compatibility/compatibility.nom b/lib/compatibility/compatibility.nom
index 4715282..01ba24f 100644
--- a/lib/compatibility/compatibility.nom
+++ b/lib/compatibility/compatibility.nom
@@ -17,7 +17,7 @@ external:
         $ACTION_UPGRADES.$version.$stub = $upgrade_fn
     
     (upgrade $tree to $version as $body) parses as
-        upgrade to $version via (($ $end_version) -> ($, with ($tree -> $body)))
+        upgrade to $version via ($ -> ($, with ($tree -> $body)))
     
     (upgrade action $actions to $version as $body) compiles to:
         if ($actions is "Action" syntax tree):
@@ -97,31 +97,31 @@ external:
         for ($v = $) in $ACTION_UPGRADES:
             $versions.$v = (yes)
         
-        $versions =
-            [: for ($v = $) in $versions: if ((Ver $v).lib == $start.lib): add $v]
+        $versions = [:
+            for ($v = $) in $versions:
+                $v2 = (Ver $v)
+                if ($v2.lib == $start.lib):
+                    if ($start.version < $v2.version <= $end.version): add $v
+        ]
         
         sort $versions by $ -> ($ as version list)
+        $curr_version = $start_version
         for $ver in $versions:
-            if (($ver as version list) <= $start.version): do next $ver
-            if (($ver as version list) > $end.version): stop $ver
-            if $ACTION_UPGRADES.$ver:
-                $tree =
-                    $tree, with
-                        $ ->:
-                            if ($ is "Action" syntax tree):
-                                $(upgrade 1 to 2) = $ACTION_UPGRADES.$ver.($.stub)
-                                if $(upgrade 1 to 2):
-                                    $with_upgraded_args = {: for ($k = $v) in $: add $k = ($v upgraded from $start_version to $end_version)}
-                                    set $with_upgraded_args's metatable to ($'s metatable)
-                                    return (upgrade $with_upgraded_args to $end_version)
+            $tree =
+                SyntaxTree
+                    {: for ($k = $v) in $tree: add $k = ($v upgraded from $curr_version to $ver)}
+            if (($tree.type == "Action") and $ACTION_UPGRADES.$ver):
+                $(upgrade 1) = $ACTION_UPGRADES.$ver.($tree, get stub)
+                if $(upgrade 1):
+                    $tree = (upgrade $tree)
+                    go to (next version)
             
             if $UPGRADES.$ver:
-                $with_upgraded_args = {:
-                    for ($k = $v) in $tree:
-                        add $k = ($v upgraded from $start_version to $end_version)
-                }
-                set $with_upgraded_args's metatable to ($tree's metatable)
-                $tree = ($UPGRADES.$ver $with_upgraded_args $end_version)
+                $tree = ($UPGRADES.$ver $tree $ver)
+                go to (next version)
+            
+            --- (next version) ---
+            $curr_version = $ver
         
         if ($tree.version != $end_version):
             $tree = (SyntaxTree {: for ($k = $v) in $tree: add $k = $v})
@@ -138,4 +138,4 @@ external:
         $tree upgraded from ($tree.version or $(NOMSU VERSION)) to $end_version
     
     ($tree upgraded) means
-        $tree upgraded from ($tree.version or $(NOMSU VERSION)) to $(NOMSU VERSION)
\ No newline at end of file
+        $tree upgraded from ($tree.version or $(NOMSU VERSION)) to $(NOMSU VERSION)