diff --git a/corpus/declarations.txt b/corpus/declarations.txt
index 79e6d73..d32d0e3 100644
--- a/corpus/declarations.txt
+++ b/corpus/declarations.txt
@@ -85,6 +85,8 @@ a {
   b: 0.5%;
   c: 5em;
   margin: 10E3px;
+  margin: -456.8px;
+  margin: -0.0px;
 }
 
 ---
@@ -93,6 +95,8 @@ a {
   (rule_set (selectors (tag_name)) (block
     (declaration (property_name) (float_value (unit)))
     (declaration (property_name) (integer_value (unit)))
+    (declaration (property_name) (float_value (unit)))
+    (declaration (property_name) (float_value (unit)))
     (declaration (property_name) (float_value (unit))))))
 
 ============================
diff --git a/grammar.js b/grammar.js
index d88c1bc..347801f 100644
--- a/grammar.js
+++ b/grammar.js
@@ -313,15 +313,15 @@ module.exports = grammar({
 
     identifier: $ => /[a-zA-Z-_][a-zA-Z0-9-_]*/,
 
-    plain_value: $ => /[a-zA-Z-_][^;()\[\]\s]*/,
-
     at_keyword: $ => /@[a-zA-Z-_]+/,
 
     comment: $ => token(seq(
       '/*',
       /[^*]*\*+([^/*][^*]*\*+)*/,
       '/'
-    ))
+    )),
+
+    plain_value: $ => /[-_]*[a-zA-Z][^;()\[\]\s]*/
   }
 })