diff --git a/src/cairo-xcb-surface-render.c b/src/cairo-xcb-surface-render.c
index b35bf4d04..044339bce 100644
--- a/src/cairo-xcb-surface-render.c
+++ b/src/cairo-xcb-surface-render.c
@@ -4470,6 +4470,9 @@ _cairo_xcb_surface_add_glyph (cairo_xcb_connection_t *connection,
 	    const uint8_t *d;
 	    uint8_t *new, *n;
 
+	    if (c == 0)
+		break;
+
 	    new = malloc (c);
 	    if (unlikely (new == NULL)) {
 		status = _cairo_error (CAIRO_STATUS_NO_MEMORY);
@@ -4498,6 +4501,9 @@ _cairo_xcb_surface_add_glyph (cairo_xcb_connection_t *connection,
 	    const uint32_t *d;
 	    uint32_t *new, *n;
 
+	    if (c == 0)
+		break;
+
 	    new = malloc (4 * c);
 	    if (unlikely (new == NULL)) {
 		status = _cairo_error (CAIRO_STATUS_NO_MEMORY);