diff --git a/indra/llcommon/llsdserialize.h b/indra/llcommon/llsdserialize.h
index cf6c1ab73a9903125f52c52baf70f4f8f5cf0b92..2f12c6d1ff60909a7fbf03bfc81e8e4d7dbd7748 100644
--- a/indra/llcommon/llsdserialize.h
+++ b/indra/llcommon/llsdserialize.h
@@ -870,7 +870,7 @@ class LL_COMMON_API LLUZipHelper : public LLRefCount
 LL_COMMON_API std::string zip_llsd(LLSD& data);
 
 
-LL_COMMON_API U8* unzip_llsdNavMesh( bool& valid, unsigned int& outsize,std::istream& is, S32 size);
+LL_COMMON_API U8* unzip_llsdNavMesh( bool& valid, size_t& outsize,std::istream& is, S32 size);
 
 // returns a pointer to the array or past the array if the deprecated header exists
 LL_COMMON_API char* strip_deprecated_header(char* in, U32& cur_size, U32* header_size = nullptr);