diff --git a/tz.cpp b/tz.cpp
index 377968f..78ef91f 100644
--- a/tz.cpp
+++ b/tz.cpp
@@ -141,7 +141,7 @@ static CONSTDATA char folder_delimiter = '/';
 
 #endif
 
-#if __GNUC__ < 5
+#if defined(__GNUC__) && __GNUC__ < 5
 // GCC 4.9 Bug 61489 Wrong warning with -Wmissing-field-initializers
 # pragma GCC diagnostic push
 # pragma GCC diagnostic ignored "-Wmissing-field-initializers"
@@ -3208,6 +3208,6 @@ locate_native_zone(const std::string& native_tz_name)
 
 }  // namespace date
 
-#if __GNUC__ < 5
+#if defined(__GNUC__) && __GNUC__ < 5
 # pragma GCC diagnostic pop
 #endif