--- a/ExternalStream.st	Fri Apr 07 16:42:20 2017 +0200
+++ b/ExternalStream.st	Fri Apr 07 16:44:06 2017 +0200
@@ -2167,12 +2167,21 @@
                      || (__INST(handleType) == @symbol(filePointer))
                      || (__INST(handleType) == @symbol(socketFilePointer))
                      || (__INST(handleType) == @symbol(pipeFilePointer))) {
-            RETURN ( __MKINT(fileno(__FILEVal(_handle))));
+            FILE *file = __FILEVal(_handle);
+            if (file != NULL) {
+                int fileNo = fileno(file);
+
+                if (fileNo >= 0) {
+                    RETURN ( __MKINT(fileNo));
+                }
+            }
         }
     }
 %}.
     handle isNil ifTrue:[^ self errorNotOpen].
     ^ self fileDescriptorOfFile:handle
+
+    "Modified: / 07-04-2017 / 16:43:54 / cg"
 !
 
 fileDescriptorOfFile:handle