diff --git a/ChangeLog b/ChangeLog
index f2e5c750..179d1f02 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2008-08-29  Nicolas François  <nicolas.francois@centraliens.net>
+
+	* src/pwconv.c, src/pwunconv.c: Fail if unexpected parameters are
+	provided.
+
 2008-08-29  Nicolas François  <nicolas.francois@centraliens.net>
 
 	* src/passwd.c: Add brackets and parenthesis.
diff --git a/src/pwconv.c b/src/pwconv.c
index ea7e64fc..475c92ae 100644
--- a/src/pwconv.c
+++ b/src/pwconv.c
@@ -118,6 +118,9 @@ int main (int argc, char **argv)
 	const struct spwd *sp;
 	struct spwd spent;
 
+	if (1 != argc) {
+		(void) fputs (_("Usage: pwconv\n"), stderr);
+	}
 	Prog = Basename (argv[0]);
 
 	(void) setlocale (LC_ALL, "");
diff --git a/src/pwunconv.c b/src/pwunconv.c
index a727bead..c0f49be3 100644
--- a/src/pwunconv.c
+++ b/src/pwunconv.c
@@ -80,6 +80,9 @@ int main (int argc, char **argv)
 	struct passwd pwent;
 	const struct spwd *spwd;
 
+	if (1 != argc) {
+		(void) fputs (_("Usage: pwunconv\n"), stderr);
+	}
 	Prog = Basename (argv[0]);
 
 	(void) setlocale (LC_ALL, "");