diff --git a/src/futils.cpp b/src/futils.cpp
index 46127e08..9486a070 100644
--- a/src/futils.cpp
+++ b/src/futils.cpp
@@ -93,7 +93,7 @@ namespace Exiv2 {
 #ifdef EXV_HAVE_STRERROR_R
         const size_t n = 1024;
 // _GNU_SOURCE: See Debian bug #485135
-# if defined EXV_STRERROR_R_CHAR_P || defined _GNU_SOURCE
+# if defined EXV_STRERROR_R_CHAR_P && defined _GNU_SOURCE
         char *buf = 0;
         char buf2[n];
         std::memset(buf2, 0x0, n);