diff --git a/library/Text/Builder.hs b/library/Text/Builder.hs
--- a/library/Text/Builder.hs
+++ b/library/Text/Builder.hs
@@ -40,17 +40,6 @@
           action2 array (offset + size1)
       size =
         size1 + size2
-  {-# INLINE mconcat #-}
-  mconcat list =
-    Builder action size
-    where
-      action =
-        Action $ \array offset -> foldlM (step array) offset list $> ()
-        where
-          step array offset (Builder (Action action) size) =
-            action array offset $> offset + size
-      size =
-        sum (map (\(Builder _ x) -> x) list)
 
 instance Semigroup Builder
 
diff --git a/tests/Main.hs b/tests/Main.hs
--- a/tests/Main.hs
+++ b/tests/Main.hs
@@ -18,8 +18,13 @@
       A.pack chars ===
       B.run (foldMap B.char chars)
     ,
-    testProperty "Concatting a list of texts is isomorphic to concatting a list of builders" $
+    testProperty "Concatting a list of texts is isomorphic to fold-mapping with builders" $
     \texts ->
       mconcat texts ===
       B.run (foldMap B.text texts)
+    ,
+    testProperty "Concatting a list of texts is isomorphic to concatting a list of builders" $
+    \texts ->
+      mconcat texts ===
+      B.run (mconcat (map B.text texts))
   ]
diff --git a/text-builder.cabal b/text-builder.cabal
--- a/text-builder.cabal
+++ b/text-builder.cabal
@@ -1,7 +1,7 @@
 name:
   text-builder
 version:
-  0.4
+  0.4.1
 category:
   Text
 synopsis: