diff --git a/libavcodec/scpr.c b/libavcodec/scpr.c
index cbe1bc40d9..ad6073dbf0 100644
--- a/libavcodec/scpr.c
+++ b/libavcodec/scpr.c
@@ -681,6 +681,8 @@ static int decompress_p(AVCodecContext *avctx,
                                 return AVERROR_INVALIDDATA;
 
                             if (bx == 0) {
+                                if (by < 2)
+                                    return AVERROR_INVALIDDATA;
                                 z = backstep;
                             } else {
                                 z = 0;
@@ -710,6 +712,8 @@ static int decompress_p(AVCodecContext *avctx,
                                 return AVERROR_INVALIDDATA;
 
                             if (bx == 0) {
+                                if (by < 2)
+                                    return AVERROR_INVALIDDATA;
                                 z = backstep;
                             } else {
                                 z = 0;