diff --git a/src/ol/source/imagewmssource.js b/src/ol/source/imagewmssource.js
index 11bdb3d591..0e48cd1bcd 100644
--- a/src/ol/source/imagewmssource.js
+++ b/src/ol/source/imagewmssource.js
@@ -1,3 +1,5 @@
+// FIXME cannot be shared between maps with different projections
+
 goog.provide('ol.source.ImageWMS');
 
 goog.require('goog.asserts');
diff --git a/src/ol/source/tilewmssource.js b/src/ol/source/tilewmssource.js
index b43d7b9b17..f9b565d426 100644
--- a/src/ol/source/tilewmssource.js
+++ b/src/ol/source/tilewmssource.js
@@ -1,5 +1,6 @@
 // FIXME add minZoom support
 // FIXME add date line wrap (tile coord transform)
+// FIXME cannot be shared between maps with different projections
 
 goog.provide('ol.source.TileWMS');