diff --git a/src/cmd/5l/span.c b/src/cmd/5l/span.c
index d3da0278bfe..338c9665bfb 100644
--- a/src/cmd/5l/span.c
+++ b/src/cmd/5l/span.c
@@ -231,7 +231,7 @@ span(void)
 				*bp++ = v;
 				*bp++ = v>>8;
 				*bp++ = v>>16;
-				*bp = v>>24;
+				*bp++ = v>>24;
 			}
 		}
 	}