diff --git a/jni/GifTranscoder.cpp b/jni/GifTranscoder.cpp
index 44fa30c..0d50770 100644
--- a/jni/GifTranscoder.cpp
+++ b/jni/GifTranscoder.cpp
@@ -274,6 +274,11 @@
                     // matches what libframesequence (Rastermill) does.
                     if (imageIndex == 0 && gifIn->SColorMap) {
                         if (gcb.TransparentColor == NO_TRANSPARENT_COLOR) {
+                            if (gifIn->SBackGroundColor < 0 ||
+                                gifIn->SBackGroundColor >= gifIn->SColorMap->ColorCount) {
+                                LOGE("SBackGroundColor overflow");
+                                return false;
+                            }
                             GifColorType bgColorIndex =
                                     gifIn->SColorMap->Colors[gifIn->SBackGroundColor];
                             bgColor = gifColorToColorARGB(bgColorIndex);