diff --git a/src/base_media_base.h b/src/base_media_base.h
--- a/src/base_media_base.h
+++ b/src/base_media_base.h
@@ -33,7 +33,7 @@ struct MD5File {
 	uint8 hash[16];              ///< md5 sum of the file
 	const char *missing_warning; ///< warning when this file is missing
 
-	ChecksumResult CheckMD5(Subdirectory subdir) const;
+	ChecksumResult CheckMD5(Subdirectory subdir, size_t max_size) const;
 };
 
 /**
@@ -129,6 +129,20 @@ struct BaseSet {
 		/* Then fall back */
 		return this->description.Begin()->second;
 	}
+
+	/**
+	 * Calculate and check the MD5 hash of the supplied file.
+	 * @param file The file get the hash of.
+	 * @param subdir The sub directory to get the files from.
+	 * @return
+	 * - #CR_MATCH if the MD5 hash matches
+	 * - #CR_MISMATCH if the MD5 does not match
+	 * - #CR_NO_FILE if the file misses
+	 */
+	static MD5File::ChecksumResult CheckMD5(const MD5File *file, Subdirectory subdir)
+	{
+		return file->CheckMD5(subdir, SIZE_MAX);
+	}
 };
 
 /**
diff --git a/src/base_media_func.h b/src/base_media_func.h
--- a/src/base_media_func.h
+++ b/src/base_media_func.h
@@ -131,7 +131,7 @@ bool BaseSet<T, Tnum_files, Tsearch_in_t
 			file->missing_warning = strdup(item->value);
 		}
 
-		switch (file->CheckMD5(BASESET_DIR)) {
+		switch (T::CheckMD5(file, BASESET_DIR)) {
 			case MD5File::CR_MATCH:
 				this->valid_files++;
 				/* FALL THROUGH */
diff --git a/src/gfxinit.cpp b/src/gfxinit.cpp
--- a/src/gfxinit.cpp
+++ b/src/gfxinit.cpp
@@ -119,7 +119,7 @@ void CheckExternalFiles()
 		/* Not all files were loaded successfully, see which ones */
 		add_pos += seprintf(add_pos, last, "Trying to load graphics set '%s', but it is incomplete. The game will probably not run correctly until you properly install this set or select another one. See section 4.1 of readme.txt.\n\nThe following files are corrupted or missing:\n", used_set->name);
 		for (uint i = 0; i < GraphicsSet::NUM_FILES; i++) {
-			MD5File::ChecksumResult res = used_set->files[i].CheckMD5(BASESET_DIR);
+			MD5File::ChecksumResult res = GraphicsSet::CheckMD5(&used_set->files[i], BASESET_DIR);
 			if (res != MD5File::CR_MATCH) add_pos += seprintf(add_pos, last, "\t%s is %s (%s)\n", used_set->files[i].filename, res == MD5File::CR_MISMATCH ? "corrupt" : "missing", used_set->files[i].missing_warning);
 		}
 		add_pos += seprintf(add_pos, last, "\n");
@@ -132,7 +132,7 @@ void CheckExternalFiles()
 		assert_compile(SoundsSet::NUM_FILES == 1);
 		/* No need to loop each file, as long as there is only a single
 		 * sound file. */
-		add_pos += seprintf(add_pos, last, "\t%s is %s (%s)\n", sounds_set->files->filename, sounds_set->files->CheckMD5(BASESET_DIR) == MD5File::CR_MISMATCH ? "corrupt" : "missing", sounds_set->files->missing_warning);
+		add_pos += seprintf(add_pos, last, "\t%s is %s (%s)\n", sounds_set->files->filename, SoundsSet::CheckMD5(sounds_set->files, BASESET_DIR) == MD5File::CR_MISMATCH ? "corrupt" : "missing", sounds_set->files->missing_warning);
 	}
 
 	if (add_pos != error_msg) ShowInfoF("%s", error_msg);
@@ -266,18 +266,21 @@ bool GraphicsSet::FillSetDetails(IniFile
 /**
  * Calculate and check the MD5 hash of the supplied filename.
  * @param subdir The sub directory to get the files from
+ * @param max_size Only calculate the hash for this many bytes from the file start.
  * @return
  * - #CR_MATCH if the MD5 hash matches
  * - #CR_MISMATCH if the MD5 does not match
  * - #CR_NO_FILE if the file misses
  */
-MD5File::ChecksumResult MD5File::CheckMD5(Subdirectory subdir) const
+MD5File::ChecksumResult MD5File::CheckMD5(Subdirectory subdir, size_t max_size) const
 {
 	size_t size;
 	FILE *f = FioFOpenFile(this->filename, "rb", subdir, &size);
 
 	if (f == NULL) return CR_NO_FILE;
 
+	size = min(size, max_size);
+
 	Md5 checksum;
 	uint8 buffer[1024];
 	uint8 digest[16];