diff --git a/gio/tests/data-input-stream.c b/gio/tests/data-input-stream.c
index 8a1e8fb28..693481777 100644
--- a/gio/tests/data-input-stream.c
+++ b/gio/tests/data-input-stream.c
@@ -80,9 +80,9 @@ test_read_lines (GDataStreamNewlineType newline_type)
     lines[i] = "some_text";
 	
   base_stream = g_memory_input_stream_new ();
-  g_assert (base_stream != NULL);
+  g_assert_nonnull (base_stream);
   stream = G_INPUT_STREAM (g_data_input_stream_new (base_stream));
-  g_assert(stream != NULL);
+  g_assert_nonnull (stream);
 	
   /*  Byte order testing */
   g_data_input_stream_set_byte_order (G_DATA_INPUT_STREAM (stream), G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN);
@@ -210,7 +210,7 @@ test_read_lines_LF_invalid_utf8 (void)
 	g_assert_no_error (error);
       else
 	{
-	  g_assert (error != NULL);
+          g_assert_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE);
 	  g_clear_error (&error);
 	  g_free (line);
 	  break;
@@ -354,7 +354,7 @@ test_read_upto (void)
               line++;
 
               stop_char = g_data_input_stream_read_byte (G_DATA_INPUT_STREAM (stream), NULL, &error);
-              g_assert (memchr (DATA_SEP, stop_char, DATA_SEP_LEN) != NULL);
+              g_assert_nonnull (memchr (DATA_SEP, stop_char, DATA_SEP_LEN));
               g_assert_no_error (error);
             }
           g_free (data);