diff --git a/src/plugins/e-acsl/man/e-acsl-gcc.sh.1 b/src/plugins/e-acsl/man/e-acsl-gcc.sh.1
index 530649ad13d9e8041868a83f79981a84e0a95537..1fad5fba936079194c65047e003fa86e2bb92403 100644
--- a/src/plugins/e-acsl/man/e-acsl-gcc.sh.1
+++ b/src/plugins/e-acsl/man/e-acsl-gcc.sh.1
@@ -176,8 +176,8 @@ Trigger failure if a NULL-pointer is used as an input to free function
 On assertion failure exit with the given integer code intead of raising an abort
 signal
 .TP
-.B --external-assert
-Set it if you provide your own implementation of e_acsl_assert
+.B --external-assert=\fI<FILE>
+the filename that contains your own implementation of __e_acsl_assert
 .TP
 .B -m, --memory-model=\fI<model>
 memory model (i.e., a runtime library for checking memory related annotations)