diff --git a/src/process.c b/src/process.c
index 1ab83780914..f4613be28ed 100644
--- a/src/process.c
+++ b/src/process.c
@@ -4859,6 +4859,10 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
              data is available in the buffers manually.  */
           if (nfds == 0)
 	    {
+	      fd_set tls_available;
+	      int set = 0;
+
+	      FD_ZERO (&tls_available);
 	      if (! wait_proc)
 		{
 		  /* We're not waiting on a specific process, so loop
@@ -4879,7 +4883,8 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
 			  {
 			    nfds++;
 			    eassert (p->infd == channel);
-			    FD_SET (p->infd, &Available);
+			    FD_SET (p->infd, &tls_available);
+			    set++;
 			  }
 		      }
 		}
@@ -4896,9 +4901,12 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
 		      nfds = 1;
 		      eassert (0 <= wait_proc->infd);
 		      /* Set to Available.  */
-		      FD_SET (wait_proc->infd, &Available);
+		      FD_SET (wait_proc->infd, &tls_available);
+		      set++;
 		    }
 		}
+	      if (set)
+		Available = tls_available;
 	    }
 #endif
 	}