diff --git a/Source/appfat.cpp b/Source/appfat.cpp
index da2c364a1..42c1f8fad 100644
--- a/Source/appfat.cpp
+++ b/Source/appfat.cpp
@@ -93,7 +93,7 @@ void FileErrDlg(const char *error)
 	    1024,
 	    "Unable to open a required file.\n"
 	    "\n"
-	    "Verify that the MD5 of diabdat.mpq matches on of the following values\n"
+	    "Verify that the MD5 of diabdat.mpq matches one of the following values\n"
 	    "011bc6518e6166206231080a4440b373\n"
 	    "68f049866b44688a7af65ba766bef75a\n"
 	    "\n"