diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Revision history for ogma-language-cocospec
 
+## [1.0.9] - 2023-05-21
+
+* Version bump 1.0.9 (#93).
+* Add unary operators ZtoPre, YtoPre (#86).
+
 ## [1.0.8] - 2023-03-21
 
 * Version bump 1.0.8 (#81).
diff --git a/grammar/CoCoSpec.cf b/grammar/CoCoSpec.cf
--- a/grammar/CoCoSpec.cf
+++ b/grammar/CoCoSpec.cf
@@ -49,12 +49,14 @@
 
 -- Boolean Operators
 
-Op1Once.   Op1Pre ::= "O"   ;
-Op1Pre.    Op1Pre ::= "pre" ;
-Op1Hist.   Op1Pre ::= "H"   ;
-Op1Y.      Op1Pre ::= "Y"   ;
-Op1Not.    Op1Pre ::= "not" ;
-Op1Bang.   Op1Pre ::= "!"   ;
+Op1Once.   Op1Pre ::= "O"      ;
+Op1Pre.    Op1Pre ::= "pre"    ;
+Op1YtoPre. Op1Pre ::= "YtoPre" ;
+Op1ZtoPre. Op1Pre ::= "ZtoPre" ;
+Op1Hist.   Op1Pre ::= "H"      ;
+Op1Y.      Op1Pre ::= "Y"      ;
+Op1Not.    Op1Pre ::= "not"    ;
+Op1Bang.   Op1Pre ::= "!"      ;
 
 Op2And.     Op2In ::= "and"     ;
 Op2Amp.     Op2In ::= "&"       ;
diff --git a/ogma-language-cocospec.cabal b/ogma-language-cocospec.cabal
--- a/ogma-language-cocospec.cabal
+++ b/ogma-language-cocospec.cabal
@@ -32,7 +32,7 @@
 build-type:          Custom
 
 name:                ogma-language-cocospec
-version:             1.0.8
+version:             1.0.9
 homepage:            http://nasa.gov
 license:             OtherLicense
 license-file:        LICENSE.pdf