diff --git a/core/math/parser/parser-tests.factor b/core/math/parser/parser-tests.factor
index 1ee3f9d220..b8b65d1334 100644
--- a/core/math/parser/parser-tests.factor
+++ b/core/math/parser/parser-tests.factor
@@ -38,6 +38,8 @@ unit-test
 
 [ 2.0 ] [ "2." string>number ] unit-test
 
+[ 255 ] [ "ff" hex> ] unit-test
+
 [ "100.0" ]
 [ "1.0e2" string>number number>string ]
 unit-test
diff --git a/core/math/parser/parser.factor b/core/math/parser/parser.factor
index 21fbf5f186..9f07a7d953 100644
--- a/core/math/parser/parser.factor
+++ b/core/math/parser/parser.factor
@@ -87,7 +87,7 @@ SYMBOL: negative?
     >byte-array 0 suffix (string>float) ;
 
 : number-char? ( char -- ? )
-    "0123456789." member? ;
+    "0123456789ABCDEFabcdef." member? ;
 
 : numeric-looking? ( str -- ? )
     "-" ?head drop