diff --git a/glorytun.c b/glorytun.c
index e346542..12402cc 100644
--- a/glorytun.c
+++ b/glorytun.c
@@ -269,15 +269,17 @@ static ssize_t fd_read_all (int fd, void *data, size_t size)
     };
 
     while (done<size) {
-        poll(&pollfd, 1, -1);
-
         ssize_t ret = fd_read(fd, data+done, size-done);
 
         if (!ret)
             break;
 
-        if (ret>0)
-            done += ret;
+        if (ret<0) {
+            poll(&pollfd, 1, -1);
+            continue;
+        }
+
+        done += ret;
     }
 
     return done;
@@ -293,15 +295,17 @@ static ssize_t fd_write_all (int fd, const void *data, size_t size)
     };
 
     while (done<size) {
-        poll(&pollfd, 1, -1);
-
         ssize_t ret = fd_write(fd, data+done, size-done);
 
         if (!ret)
             break;
 
-        if (ret>0)
-            done += ret;
+        if (ret<0) {
+            poll(&pollfd, 1, -1);
+            continue;
+        }
+
+        done += ret;
     }
 
     return done;