diff --git a/lib/common/zbuff.h b/lib/common/zbuff.h
index 65f01e56..7820db26 100644
--- a/lib/common/zbuff.h
+++ b/lib/common/zbuff.h
@@ -185,7 +185,7 @@ ZSTDLIB_API ZBUFF_DCtx* ZBUFF_createDCtx_advanced(ZSTD_customMem customMem);
 /*--- Advanced Streaming function ---*/
 ZSTDLIB_API size_t ZBUFF_compressInit_advanced(ZBUFF_CCtx* zbc,
                                                const void* dict, size_t dictSize,
-                                               ZSTD_parameters params, U64 pledgedSrcSize);
+                                               ZSTD_parameters params, unsigned long long pledgedSrcSize);
 
 #endif /* ZBUFF_STATIC_LINKING_ONLY */
 
diff --git a/lib/compress/zbuff_compress.c b/lib/compress/zbuff_compress.c
index ef8448ce..837d22cf 100644
--- a/lib/compress/zbuff_compress.c
+++ b/lib/compress/zbuff_compress.c
@@ -137,7 +137,7 @@ size_t ZBUFF_freeCCtx(ZBUFF_CCtx* zbc)
 
 size_t ZBUFF_compressInit_advanced(ZBUFF_CCtx* zbc,
                                    const void* dict, size_t dictSize,
-                                   ZSTD_parameters params, U64 pledgedSrcSize)
+                                   ZSTD_parameters params, unsigned long long pledgedSrcSize)
 {
     /* allocate buffers */
     {   size_t const neededInBuffSize = (size_t)1 << params.cParams.windowLog;