diff --git a/src/dff/wrsac.c b/src/dff/wrsac.c
index 0d9555b..be4a075 100755
--- a/src/dff/wrsac.c
+++ b/src/dff/wrsac.c
@@ -114,6 +114,7 @@ wrsac(int   idfl,
             if(*nerr != SAC_OK) {
               goto L_8888;
             }
+        lseek(-nun, SEEK_SET, 0);
 	}
 
 	/* - Write the header */