diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index f2cbbc22..df8201be 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -2830,7 +2830,7 @@ size_t ZSTD_freeCStream(ZSTD_CStream* zcs)
 size_t ZSTD_CStreamInSize(void)  { return ZSTD_BLOCKSIZE_ABSOLUTEMAX; }
 size_t ZSTD_CStreamOutSize(void) { return ZSTD_compressBound(ZSTD_BLOCKSIZE_ABSOLUTEMAX) + ZSTD_blockHeaderSize + 4 /* 32-bits hash */ ; }
 
-size_t ZSTD_resetCStream(ZSTD_CStream* zcs, U64 pledgedSrcSize)
+size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize)
 {
     CHECK_F(ZSTD_compressBegin_usingCDict(zcs->cctx, zcs->cdict, pledgedSrcSize));