diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Revision history for typst-hs
 
+## 0.8.0.1
+
+  * Fix subtracting units, e.g. `1mm-0mm` (#71, Luke Grehan).
+
 ## 0.8
 
   * Allow `json`, `toml`, `xml` to take either file path or bytes.
diff --git a/src/Typst/Parse.hs b/src/Typst/Parse.hs
--- a/src/Typst/Parse.hs
+++ b/src/Typst/Parse.hs
@@ -989,14 +989,14 @@
 pUnit :: P Unit
 pUnit =
   (Percent <$ sym "%")
-    <|> (Pt <$ pKeyword "pt")
-    <|> (Mm <$ pKeyword "mm")
-    <|> (Cm <$ pKeyword "cm")
-    <|> (In <$ pKeyword "in")
-    <|> (Deg <$ pKeyword "deg")
-    <|> (Rad <$ pKeyword "rad")
-    <|> (Em <$ pKeyword "em")
-    <|> (Fr <$ pKeyword "fr")
+    <|> (Pt <$ sym "pt")
+    <|> (Mm <$ sym "mm")
+    <|> (Cm <$ sym "cm")
+    <|> (In <$ sym "in")
+    <|> (Deg <$ sym "deg")
+    <|> (Rad <$ sym "rad")
+    <|> (Em <$ sym "em")
+    <|> (Fr <$ sym "fr")
 
 pIdent :: P Expr
 pIdent = Ident <$> pIdentifier
diff --git a/test/typ/compiler/set-08.out b/test/typ/compiler/set-08.out
new file mode 100644
--- /dev/null
+++ b/test/typ/compiler/set-08.out
@@ -0,0 +1,60 @@
+--- parse tree ---
+[ Code
+    "typ/compiler/set-08.typ"
+    ( line 1 , column 2 )
+    (Let
+       (BasicBind (Just (Identifier "test")))
+       (FuncExpr
+          [ NormalParam (Identifier "x") , NormalParam (Identifier "y") ]
+          (Block
+             (CodeBlock
+                [ If
+                    [ ( Equals (Ident (Identifier "x")) (Ident (Identifier "y"))
+                      , Block (Content [ Text "\9989" ])
+                      )
+                    , ( Literal (Boolean True)
+                      , Block
+                          (Content
+                             [ Text "\10060"
+                             , Text "("
+                             , Code
+                                 "typ/compiler/set-08.typ"
+                                 ( line 1 , column 47 )
+                                 (FuncCall
+                                    (Ident (Identifier "repr"))
+                                    [ NormalArg (Ident (Identifier "x")) ])
+                             , Space
+                             , Text "/"
+                             , Text "="
+                             , Space
+                             , Code
+                                 "typ/compiler/set-08.typ"
+                                 ( line 1 , column 59 )
+                                 (FuncCall
+                                    (Ident (Identifier "repr"))
+                                    [ NormalArg (Ident (Identifier "y")) ])
+                             , Text ")"
+                             ])
+                      )
+                    ]
+                ]))))
+, SoftBreak
+, Code
+    "typ/compiler/set-08.typ"
+    ( line 2 , column 2 )
+    (Set
+       (Ident (Identifier "page"))
+       [ KeyValArg
+           (Identifier "margin")
+           (Minus (Literal (Numeric 1.0 Mm)) (Literal (Numeric 0.0 Mm)))
+       ])
+, SoftBreak
+, Text "foo"
+, ParBreak
+]
+--- evaluated ---
+document(body: { text(body: [
+]), 
+                 text(body: [
+foo]), 
+                 parbreak() })
diff --git a/test/typ/compiler/set-08.typ b/test/typ/compiler/set-08.typ
new file mode 100644
--- /dev/null
+++ b/test/typ/compiler/set-08.typ
@@ -0,0 +1,2 @@
+#set page(margin: 1mm-0mm)
+foo
diff --git a/typst.cabal b/typst.cabal
--- a/typst.cabal
+++ b/typst.cabal
@@ -1,6 +1,6 @@
 cabal-version:      2.4
 name:               typst
-version:            0.8
+version:            0.8.0.1
 synopsis:           Parsing and evaluating typst syntax.
 description:        A library for parsing and evaluating typst syntax.
                     Typst (<https://typst.app>) is a document layout and