diff --git a/Include/LogicLib.nsh b/Include/LogicLib.nsh
index d4e44698..326417a2 100644
--- a/Include/LogicLib.nsh
+++ b/Include/LogicLib.nsh
@@ -19,7 +19,7 @@
 ;       AndIf|AndIfNot|AndUnless|OrIf|OrIfNot|OrUnless
 ;         - Adds any number of extra conditions to If, IfNot, Unless, ElseIf,
 ;           ElseIfNot and ElseUnless statements.
-;       IfThen..|..|
+;       IfThen|IfNotThen..|..|
 ;         - Conditionally executes an inline statement, depending on the value
 ;           of an expression.
 ;       IfCmd..||..|
@@ -461,6 +461,16 @@
   !macroend
   !define IfThen `!insertmacro _IfThen`
 
+  !macro _IfNotThen _a _o _b _t
+    !verbose push
+    !verbose ${LOGICLIB_VERBOSITY}
+    ${IfNot} `${_a}` `${_o}` `${_b}`
+      ${_t}
+    ${EndIf}
+    !verbose pop
+  !macroend
+  !define IfNotThen `!insertmacro _IfNotThen`
+
   !macro _ForEach _v _f _t _o _s
     !verbose push
     !verbose ${LOGICLIB_VERBOSITY}