diff --git a/dep/libchdr/src/libchdr_chd.c b/dep/libchdr/src/libchdr_chd.c
index 6ee62ce3a..bd06c53c8 100644
--- a/dep/libchdr/src/libchdr_chd.c
+++ b/dep/libchdr/src/libchdr_chd.c
@@ -89,6 +89,11 @@
 
 #define CHD_V1_SECTOR_SIZE			512			/* size of a "sector" in the V1 header */
 
+#define CHD_MAX_HUNK_SIZE				(128 * 1024 * 1024) /* hunk size probably shouldn't be more than 128MB */
+
+/* we're currently only using this for CD/DVDs, if we end up with more than 10GB data, it's probably invalid */
+#define CHD_MAX_FILE_SIZE				(10ULL * 1024 * 1024 * 1024)
+
 #define COOKIE_VALUE				0xbaadf00d
 #define MAX_ZLIB_ALLOCS				64
 
@@ -2587,12 +2592,8 @@ static chd_error header_validate(const chd_header *header)
 			return CHDERR_INVALID_PARAMETER;
 	}
 
-	/* some basic size checks to prevent huge mallocs: hunk size probably shouldn't be more than 128MB */
-	if (header->hunkbytes >= (128 * 1024 * 1024))
-		return CHDERR_INVALID_PARAMETER;
-
-	/* - we're currently only using this for CD/DVDs, if we end up with more than 10GB data, it's probably invalid */
-	if (((uint64_t)header->hunkbytes * (uint64_t)header->totalhunks) >= (10ULL * 1024 * 1024 * 1024))
+	/* some basic size checks to prevent huge mallocs */
+	if (header->hunkbytes >= CHD_MAX_HUNK_SIZE || ((uint64_t)header->hunkbytes * (uint64_t)header->totalhunks) >= CHD_MAX_FILE_SIZE)
 		return CHDERR_INVALID_PARAMETER;
 
 	return CHDERR_NONE;
diff --git a/src/util/cd_image_chd.cpp b/src/util/cd_image_chd.cpp
index 42e575de6..94e3cbfce 100644
--- a/src/util/cd_image_chd.cpp
+++ b/src/util/cd_image_chd.cpp
@@ -453,8 +453,9 @@ CDImage::PrecacheResult CDImageCHD::Precache(ProgressCallback* progress)
   progress->SetProgressRange(100);
 
   auto callback = [](size_t pos, size_t total, void* param) {
-    const u32 percent = static_cast<u32>((pos * 100) / total);
-    static_cast<ProgressCallback*>(param)->SetProgressValue(std::min<u32>(percent, 100));
+    constexpr size_t one_mb = 1048576;
+    static_cast<ProgressCallback*>(param)->SetProgressRange(static_cast<u32>((total + (one_mb - 1)) / one_mb));
+    static_cast<ProgressCallback*>(param)->SetProgressValue(static_cast<u32>((pos + (one_mb - 1)) / one_mb));
   };
 
   if (chd_precache_progress(m_chd, callback, progress) != CHDERR_NONE)