diff --git a/doc/manual/source/the-model-file.rst b/doc/manual/source/the-model-file.rst
index 7d919ac004609d7dbfbbbbc79a1f8159619e05ea..8d12265c623dffdeab799f761818a3c92fb09f4d 100644
--- a/doc/manual/source/the-model-file.rst
+++ b/doc/manual/source/the-model-file.rst
@@ -3883,7 +3883,7 @@ speed-up on large models.
        .. math::
              LB = X   &\Rightarrow   F(X)>0\\
  
-             LB\leq X \leq UB &\Rightarrow   F(X)=0\\
+             LB < X < UB &\Rightarrow   F(X)=0\\
 
              X =UB &\Rightarrow   F(X)<0.