diff --git a/include/llvm/Support/DataTypes.h.in b/include/llvm/Support/DataTypes.h.in
index 6b3aee8ce62..c218193b932 100644
--- a/include/llvm/Support/DataTypes.h.in
+++ b/include/llvm/Support/DataTypes.h.in
@@ -36,15 +36,12 @@
 @INCLUDE_INTTYPES_H@
 @INCLUDE_SYS_TYPES_H@
 @INCLUDE_STDINT_H@
-
-// Handle incorrect definition of uint64_t as u_int64_t
-#ifndef HAVE_UINT64_T
-#ifdef HAVE_U_INT64_T
+// Interix has u_int64_t, but not uint64_t
+#if !defined(HAVE_UINT64_T) && defined(HAVE_U_INT64_T)
 typedef u_int64_t uint64_t;
 #else
 # error "Don't have a definition for uint64_t on this platform"
 #endif
-#endif
 
 #else
 // Visual C++ doesn't provide standard integer headers, but it does provide