diff --git a/cderror.h b/cderror.h
index 77b8eb64..e7ac9d99 100644
--- a/cderror.h
+++ b/cderror.h
@@ -127,6 +127,8 @@ JMESSAGE(JERR_UNSUPPORTED_FORMAT, "Unsupported output file format")
 JMESSAGE(JERR_PNG_ERROR, "Unable to read PNG file: %s")
 #endif
 
+JMESSAGE(JERR_UNSUPPORTED_SUSPEND, "I/O suspension not supported in scan optimization")
+
 #ifdef JMAKE_ENUM_LIST
 
   JMSG_LASTADDONCODE
diff --git a/jcmaster.c b/jcmaster.c
index bf5bf2f5..938e058b 100644
--- a/jcmaster.c
+++ b/jcmaster.c
@@ -605,7 +605,9 @@ copy_buffer (j_compress_ptr cinfo, int scan_idx)
     size -= cinfo->dest->free_in_buffer;
     cinfo->dest->next_output_byte += cinfo->dest->free_in_buffer;
     cinfo->dest->free_in_buffer = 0;
-    (*cinfo->dest->empty_output_buffer)(cinfo);
+    
+    if (!(*cinfo->dest->empty_output_buffer)(cinfo))
+      ERREXIT(cinfo, JERR_UNSUPPORTED_SUSPEND);
   }
 
   MEMCOPY(cinfo->dest->next_output_byte, src, size);