--- a/src/toplev.cc
+++ b/src/toplev.cc
@@ -70,6 +70,7 @@
 #include "pt-plot.h"
 #include "sighandlers.h"
 #include "sysdep.h"
+#include "syswait.h"
 #include "toplev.h"
 #include "unwind-prot.h"
 #include "utils.h"
@@ -649,9 +650,13 @@
 
 // Execute a shell command.
 
+static sigset_t signal_set, old_signal_set;
+
 static void
 cleanup_iprocstream (void *p)
 {
+  UNBLOCK_CHILD (old_signal_set);
+
   delete (iprocstream *) p;
 }
 
@@ -660,6 +665,8 @@
 {
   octave_value_list retval;
 
+  BLOCK_CHILD (signal_set, old_signal_set);
+
   iprocstream *cmd = new iprocstream (cmd_str.c_str ());
 
   add_unwind_protect (cleanup_iprocstream, cmd);
@@ -680,8 +687,8 @@
       // process exited normally, extract the actual exit status of
       // the command.  Otherwise, return 127 as a failure code.
 
-      if ((status & 0xff) == 0)
-	status = (status >> 8) & 0xff;
+      if (WIFEXITED (status))
+	status = WEXITSTATUS (status);
 
       output_buf << ends;
 
@@ -787,8 +794,8 @@
 	      // status of the command.  Otherwise, return 127 as a
 	      // failure code.
 
-	      if ((status & 0xff) == 0)
-		status = (status >> 8) & 0xff;
+	      if (WIFEXITED (status))
+		status = WEXITSTATUS (status);
 
 	      retval = (double) status;
 	    }