diff --git a/unsupported/test/mpreal/mpreal.h b/unsupported/test/mpreal/mpreal.h
index 9b0cf7268..8404f1ff8 100644
--- a/unsupported/test/mpreal/mpreal.h
+++ b/unsupported/test/mpreal/mpreal.h
@@ -99,7 +99,7 @@
 
 // Detect support for explicit converters.
 #if (__has_feature(cxx_explicit_conversions) || \
-       (defined(__GXX_EXPERIMENTAL_CXX0X__) && __GNUC_MINOR >= 5) || __cplusplus >= 201103L || \
+       (defined(__GXX_EXPERIMENTAL_CXX0X__) && __GNUC_MINOR__ >= 5) || __cplusplus >= 201103L || \
        (defined(_MSC_VER) && _MSC_VER >= 1800))
 
     #define MPREAL_HAVE_EXPLICIT_CONVERTERS