diff --git a/internal/spec/grammar.pegn b/internal/spec/grammar.pegn
index d76f0a8..028f33f 100644
--- a/internal/spec/grammar.pegn
+++ b/internal/spec/grammar.pegn
@@ -25,7 +25,7 @@ ValueLogExpAnd <-- AttrExp SP* And SP* AttrExp
 ValueFilterNot <-- Not SP* '(' SP* ValueFilter SP* ')'
 
 Not   <- ('n' / 'N') ('o' / 'O') / ('t' / 'T')
-Or    <- ('o' / 'R') ('r' / 'R')
+Or    <- ('o' / 'O') ('r' / 'R')
 And   <- ('a' / 'A') ('n' / 'N') ('d' / 'D')
 
 Pr    <- ('p' / 'P') ('r' / 'R')
@@ -70,4 +70,4 @@ Escaped    <- '"'
             / 'u' ([0-9] / [A-F]){4}
 
 # A customized/simplified version of the URI specified in RFC3986.
-Uri <-- (([a-z] / [A-Z] / [0-9] / '.')+ ':')+
\ No newline at end of file
+Uri <-- (([a-z] / [A-Z] / [0-9] / '.')+ ':')+