diff --git a/lib/libc/stdlib/merge.c b/lib/libc/stdlib/merge.c
index a47e3007290..e188dfe1a1a 100644
--- a/lib/libc/stdlib/merge.c
+++ b/lib/libc/stdlib/merge.c
@@ -111,6 +111,9 @@ mergesort(base, nmemb, size, cmp)
 		return (-1);
 	}
 
+	if (nmemb == 0)
+		return (0);
+
 	/*
 	 * XXX
 	 * Stupid subtraction for the Cray.