diff --git a/phino.cabal b/phino.cabal
--- a/phino.cabal
+++ b/phino.cabal
@@ -1,7 +1,7 @@
 cabal-version:      3.0
 
 name:               phino
-version:            0.0.0.24
+version:            0.0.0.25
 license:            MIT
 synopsis:           Command-Line Manipulator of 𝜑-Calculus Expressions
 description:        Please see the README on GitHub at <https://github.com/objectionary/phino#readme>
diff --git a/src/Rewriter.hs b/src/Rewriter.hs
--- a/src/Rewriter.hs
+++ b/src/Rewriter.hs
@@ -102,7 +102,7 @@
     _rewrite prog count = do
       let depth = _maxDepth ctx
           must = _must ctx
-      if must /= 0 && count > must
+      if must /= 0 && count - 1 > must
         then throwIO (ContinueAfter must)
         else
           if count - 1 == depth
@@ -115,7 +115,7 @@
               if rewritten == prog
                 then do
                   logDebug "No rule matched, rewriting is stopped"
-                  if must /= 0 && count /= must
-                    then throwIO (StoppedBefore must count)
+                  if must /= 0 && count - 1 /= must
+                    then throwIO (StoppedBefore must (count - 1))
                     else pure rewritten
                 else _rewrite rewritten (count + 1)
diff --git a/src/Rule.hs b/src/Rule.hs
--- a/src/Rule.hs
+++ b/src/Rule.hs
@@ -161,6 +161,7 @@
   where
     partOf :: Expression -> [Binding] -> Bool
     partOf expr [] = False
+    partOf expr (BiTau _ (ExFormation bds) : rest) = expr == ExFormation bds || partOf expr bds || partOf expr rest
     partOf expr (BiTau _ expr' : rest) = expr == expr' || partOf expr rest
     partOf expr (bd : rest) = partOf expr rest
 
diff --git a/test/CLISpec.hs b/test/CLISpec.hs
--- a/test/CLISpec.hs
+++ b/test/CLISpec.hs
@@ -178,13 +178,15 @@
           ["rewrite", "--nothing", "--output=xmir", "--omit-listing"]
           ["<?xml version=\"1.0\" encoding=\"UTF-8\"?>", "<object", "<listing>4 lines of phi</listing>", "  <o base=\"Q.y\" name=\"x\"/>"]
 
-    it "fails with --nothing and --must=2" $
-      withStdin "Q -> [[ ]]" $
-        testCLIFailed ["rewrite", "--nothing", "--must=2"] "it's expected exactly 2 rewriting cycles happened, but rewriting stopped after 1"
+    it "does not fail on exactly 1 rewrtingin" $
+      withStdin "{⟦ t ↦ ⟦ x ↦ \"foo\" ⟧ ⟧}" $
+        testCLI
+          ["rewrite", "--rule=test-resources/cli/simple.yaml", "--must=1", "--sweet"]
+          ["x ↦ \"bar\""]
 
-    it "does not fail with --nothing and --must" $
+    it "fails with --nothing and --must" $
       withStdin "Q -> [[ ]]" $
-        testCLI ["rewrite", "--nothing", "--must"] ["Φ ↦ ⟦ ρ ↦ ∅ ⟧"]
+        testCLIFailed ["rewrite", "--nothing", "--must"] "it's expected exactly 1 rewriting cycles happened, but rewriting stopped after 0"
 
     it "fails with --normalize and --must" $
       withStdin "Q -> [[ x -> [[ y -> 5 ]].y ]].x" $