diff --git a/Modular_arithmetic/doc_tex/Modular_arithmetic_ref/Modular.tex b/Modular_arithmetic/doc_tex/Modular_arithmetic_ref/Modular.tex
index 991b93256e1..66b3c742595 100644
--- a/Modular_arithmetic/doc_tex/Modular_arithmetic_ref/Modular.tex
+++ b/Modular_arithmetic/doc_tex/Modular_arithmetic_ref/Modular.tex
@@ -18,6 +18,8 @@ Since the type is base on double
 arithmetic the prime is restricted to values less than $2^{26}$. 
 The initial value of $p$ is 67111067. 
 
+Note that due to the static prime the type is not thread-safe.
+
 \ccInclude{CGAL/Modular.h}
 
 \ccIsModel