diff --git a/expressions/scanner.go b/expressions/scanner.go
index ca3f5fd..312cb05 100644
--- a/expressions/scanner.go
+++ b/expressions/scanner.go
@@ -22,10 +22,10 @@ var _expression_actions []byte = []byte{
 var _expression_key_offsets []byte = []byte{
 	0, 1, 2, 3, 4, 5, 6, 7, 
 	8, 9, 10, 12, 37, 40, 41, 42, 
-	44, 45, 48, 50, 53, 54, 55, 63, 
-	72, 81, 90, 99, 108, 117, 126, 135, 
-	144, 154, 163, 172, 181, 190, 199, 208, 
-	217, 
+	44, 45, 48, 50, 53, 54, 55, 64, 
+	74, 84, 94, 104, 114, 124, 134, 144, 
+	154, 165, 175, 185, 195, 205, 215, 225, 
+	235, 
 }
 
 var _expression_trans_keys []byte = []byte{
@@ -35,38 +35,40 @@ var _expression_trans_keys []byte = []byte{
 	105, 111, 116, 9, 13, 48, 57, 60, 
 	62, 65, 90, 98, 122, 32, 9, 13, 
 	61, 34, 97, 108, 39, 46, 48, 57, 
-	48, 57, 46, 48, 57, 61, 61, 58, 
-	95, 48, 57, 65, 90, 97, 122, 58, 
+	48, 57, 46, 48, 57, 61, 61, 45, 
+	58, 95, 48, 57, 65, 90, 97, 122, 
+	45, 58, 95, 110, 48, 57, 65, 90, 
+	97, 122, 45, 58, 95, 100, 48, 57, 
+	65, 90, 97, 122, 45, 58, 95, 111, 
+	48, 57, 65, 90, 97, 122, 45, 58, 
 	95, 110, 48, 57, 65, 90, 97, 122, 
-	58, 95, 100, 48, 57, 65, 90, 97, 
-	122, 58, 95, 111, 48, 57, 65, 90, 
-	97, 122, 58, 95, 110, 48, 57, 65, 
-	90, 97, 122, 58, 95, 116, 48, 57, 
-	65, 90, 97, 122, 58, 95, 97, 48, 
-	57, 65, 90, 98, 122, 58, 95, 105, 
-	48, 57, 65, 90, 97, 122, 58, 95, 
-	110, 48, 57, 65, 90, 97, 122, 58, 
-	95, 115, 48, 57, 65, 90, 97, 122, 
-	58, 95, 97, 111, 48, 57, 65, 90, 
-	98, 122, 58, 95, 108, 48, 57, 65, 
-	90, 97, 122, 58, 95, 115, 48, 57, 
-	65, 90, 97, 122, 58, 95, 101, 48, 
-	57, 65, 90, 97, 122, 58, 95, 114, 
-	48, 57, 65, 90, 97, 122, 58, 95, 
-	110, 48, 57, 65, 90, 97, 122, 58, 
-	95, 114, 48, 57, 65, 90, 97, 122, 
+	45, 58, 95, 116, 48, 57, 65, 90, 
+	97, 122, 45, 58, 95, 97, 48, 57, 
+	65, 90, 98, 122, 45, 58, 95, 105, 
+	48, 57, 65, 90, 97, 122, 45, 58, 
+	95, 110, 48, 57, 65, 90, 97, 122, 
+	45, 58, 95, 115, 48, 57, 65, 90, 
+	97, 122, 45, 58, 95, 97, 111, 48, 
+	57, 65, 90, 98, 122, 45, 58, 95, 
+	108, 48, 57, 65, 90, 97, 122, 45, 
+	58, 95, 115, 48, 57, 65, 90, 97, 
+	122, 45, 58, 95, 101, 48, 57, 65, 
+	90, 97, 122, 45, 58, 95, 114, 48, 
+	57, 65, 90, 97, 122, 45, 58, 95, 
+	110, 48, 57, 65, 90, 97, 122, 45, 
 	58, 95, 114, 48, 57, 65, 90, 97, 
-	122, 58, 95, 117, 48, 57, 65, 90, 
-	97, 122, 
+	122, 45, 58, 95, 114, 48, 57, 65, 
+	90, 97, 122, 45, 58, 95, 117, 48, 
+	57, 65, 90, 97, 122, 
 }
 
 var _expression_single_lengths []byte = []byte{
 	1, 1, 1, 1, 1, 1, 1, 1, 
 	1, 1, 0, 15, 1, 1, 1, 2, 
-	1, 1, 0, 1, 1, 1, 2, 3, 
-	3, 3, 3, 3, 3, 3, 3, 3, 
-	4, 3, 3, 3, 3, 3, 3, 3, 
-	3, 
+	1, 1, 0, 1, 1, 1, 3, 4, 
+	4, 4, 4, 4, 4, 4, 4, 4, 
+	5, 4, 4, 4, 4, 4, 4, 4, 
+	4, 
 }
 
 var _expression_range_lengths []byte = []byte{
@@ -81,10 +83,10 @@ var _expression_range_lengths []byte = []byte{
 var _expression_index_offsets []byte = []byte{
 	0, 2, 4, 6, 8, 10, 12, 14, 
 	16, 18, 20, 22, 43, 46, 48, 50, 
-	53, 55, 58, 60, 63, 65, 67, 73, 
-	80, 87, 94, 101, 108, 115, 122, 129, 
-	136, 144, 151, 158, 165, 172, 179, 186, 
-	193, 
+	53, 55, 58, 60, 63, 65, 67, 74, 
+	82, 90, 98, 106, 114, 122, 130, 138, 
+	146, 155, 163, 171, 179, 187, 195, 203, 
+	211, 
 }
 
 var _expression_indicies []byte = []byte{
@@ -96,24 +98,26 @@ var _expression_indicies []byte = []byte{
 	24, 24, 13, 14, 14, 31, 33, 32, 
 	2, 1, 34, 35, 32, 2, 11, 36, 
 	21, 32, 12, 37, 12, 21, 38, 39, 
-	32, 40, 32, 41, 24, 24, 24, 24, 
-	37, 41, 24, 43, 24, 24, 24, 42, 
-	41, 24, 44, 24, 24, 24, 42, 41, 
-	24, 45, 24, 24, 24, 42, 41, 24, 
-	46, 24, 24, 24, 42, 41, 24, 47, 
-	24, 24, 24, 42, 41, 24, 48, 24, 
-	24, 24, 42, 41, 24, 49, 24, 24, 
-	24, 42, 41, 24, 50, 24, 24, 24, 
-	42, 41, 24, 51, 24, 24, 24, 42, 
-	41, 24, 52, 53, 24, 24, 24, 42, 
-	41, 24, 54, 24, 24, 24, 42, 41, 
-	24, 55, 24, 24, 24, 42, 41, 24, 
-	56, 24, 24, 24, 42, 41, 24, 57, 
-	24, 24, 24, 42, 41, 24, 58, 24, 
-	24, 24, 42, 41, 24, 59, 24, 24, 
-	24, 42, 41, 24, 60, 24, 24, 24, 
-	42, 41, 24, 55, 24, 24, 24, 42, 
-	
+	32, 40, 32, 24, 41, 24, 24, 24, 
+	24, 37, 24, 41, 24, 43, 24, 24, 
+	24, 42, 24, 41, 24, 44, 24, 24, 
+	24, 42, 24, 41, 24, 45, 24, 24, 
+	24, 42, 24, 41, 24, 46, 24, 24, 
+	24, 42, 24, 41, 24, 47, 24, 24, 
+	24, 42, 24, 41, 24, 48, 24, 24, 
+	24, 42, 24, 41, 24, 49, 24, 24, 
+	24, 42, 24, 41, 24, 50, 24, 24, 
+	24, 42, 24, 41, 24, 51, 24, 24, 
+	24, 42, 24, 41, 24, 52, 53, 24, 
+	24, 24, 42, 24, 41, 24, 54, 24, 
+	24, 24, 42, 24, 41, 24, 55, 24, 
+	24, 24, 42, 24, 41, 24, 56, 24, 
+	24, 24, 42, 24, 41, 24, 57, 24, 
+	24, 24, 42, 24, 41, 24, 58, 24, 
+	24, 24, 42, 24, 41, 24, 59, 24, 
+	24, 24, 42, 24, 41, 24, 60, 24, 
+	24, 24, 42, 24, 41, 24, 55, 24, 
+	24, 24, 42, 
 }
 
 var _expression_trans_targs []byte = []byte{
@@ -192,7 +196,7 @@ func newLexer(data []byte) *lexer {
 			pe: len(data),
 	}
 	
-//line scanner.go:196
+//line scanner.go:200
 	{
 	 lex.cs = expression_start
 	 lex.ts = 0
@@ -209,7 +213,7 @@ func (lex *lexer) Lex(out *yySymType) int {
 	tok := 0
 
 	
-//line scanner.go:213
+//line scanner.go:217
 	{
 	var _klen int
 	var _trans int
@@ -229,7 +233,7 @@ _resume:
 //line NONE:1
  lex.ts = ( lex.p)
 
-//line scanner.go:233
+//line scanner.go:237
 		}
 	}
 
@@ -310,33 +314,33 @@ _eof_trans:
 //line scanner.rl:40
  lex.act = 6;
 		case 5:
-//line scanner.rl:91
+//line scanner.rl:94
  lex.act = 10;
 		case 6:
-//line scanner.rl:92
+//line scanner.rl:95
  lex.act = 11;
 		case 7:
-//line scanner.rl:93
+//line scanner.rl:96
  lex.act = 12;
 		case 8:
-//line scanner.rl:94
+//line scanner.rl:97
  lex.act = 13;
 		case 9:
-//line scanner.rl:95
+//line scanner.rl:98
  lex.act = 14;
 		case 10:
 //line scanner.rl:45
  lex.act = 16;
 		case 11:
-//line scanner.rl:99
+//line scanner.rl:102
  lex.act = 18;
 		case 12:
-//line scanner.rl:82
+//line scanner.rl:85
  lex.te = ( lex.p)+1
 { tok = ASSIGN; ( lex.p)++; goto _out
  }
 		case 13:
-//line scanner.rl:83
+//line scanner.rl:86
  lex.te = ( lex.p)+1
 { tok = LOOP; ( lex.p)++; goto _out
  }
@@ -351,12 +355,12 @@ _eof_trans:
 
 		}
 		case 15:
-//line scanner.rl:88
+//line scanner.rl:91
  lex.te = ( lex.p)+1
 { tok = EQ; ( lex.p)++; goto _out
  }
 		case 16:
-//line scanner.rl:89
+//line scanner.rl:92
  lex.te = ( lex.p)+1
 { tok = NEQ; ( lex.p)++; goto _out
  }
@@ -366,12 +370,12 @@ _eof_trans:
 { tok = RELATION; out.name = lex.token(); ( lex.p)++; goto _out
  }
 		case 18:
-//line scanner.rl:96
+//line scanner.rl:99
  lex.te = ( lex.p)+1
 { tok = KEYWORD; out.name = string(lex.data[lex.ts:lex.te-1]); ( lex.p)++; goto _out
  }
 		case 19:
-//line scanner.rl:99
+//line scanner.rl:102
  lex.te = ( lex.p)+1
 { tok = int(lex.data[lex.ts]); ( lex.p)++; goto _out
  }
@@ -400,18 +404,18 @@ _eof_trans:
 
 		}
 		case 22:
-//line scanner.rl:98
+//line scanner.rl:101
  lex.te = ( lex.p)
 ( lex.p)--
 
 		case 23:
-//line scanner.rl:99
+//line scanner.rl:102
  lex.te = ( lex.p)
 ( lex.p)--
 { tok = int(lex.data[lex.ts]); ( lex.p)++; goto _out
  }
 		case 24:
-//line scanner.rl:99
+//line scanner.rl:102
 ( lex.p) = ( lex.te) - 1
 { tok = int(lex.data[lex.ts]); ( lex.p)++; goto _out
  }
@@ -472,7 +476,7 @@ _eof_trans:
  }
 	}
 	
-//line scanner.go:476
+//line scanner.go:480
 		}
 	}
 
@@ -486,7 +490,7 @@ _again:
 //line NONE:1
  lex.ts = 0
 
-//line scanner.go:490
+//line scanner.go:494
 		}
 	}
 
@@ -505,7 +509,7 @@ _again:
 	_out: {}
 	}
 
-//line scanner.rl:103
+//line scanner.rl:106
 
 
 	return tok
diff --git a/expressions/scanner.rl b/expressions/scanner.rl
index 9fcd493..82199d6 100644
--- a/expressions/scanner.rl
+++ b/expressions/scanner.rl
@@ -73,7 +73,10 @@ func (lex *lexer) Lex(out *yySymType) int {
 		}
 		action Relation { tok = RELATION; out.name = lex.token(); fbreak; }
 
-		ident = (alpha | '_') . (alnum | '_')* ;
+		# TODO this allows medial '-' because some themes allow it in properties.
+		# Is this a general feature of Liquid identifiers, or is it limited to
+		# property names?
+		ident = (alpha | '_') . (alnum | '_' | '-')* ;
 		int = '-'? digit+ ;
 		float = '-'? (digit+ '.' digit* | '.' digit+) ;
 		string = '"' (any - '"')* '"' | "'" (any - "'")* "'" ; # TODO escapes