1 files changed, 3 insertions, 0 deletions
diff --git a/src/library_sdl.js b/src/library_sdl.js
index 7fad5941..75544765 100644
--- a/src/library_sdl.js
+++ b/src/library_sdl.js
@@ -549,6 +549,9 @@ var LibrarySDL = {
       var h = fontData.size;
       var fontString = h + 'px ' + fontData.name;
       var tempCtx = SDL.ttfContext;
+#if ASSERTIONS
+      assert(tempCtx, 'TTF_Init must have been called');
+#endif
       tempCtx.save();
       tempCtx.font = fontString;
       var ret = tempCtx.measureText(text).width | 0;