diff --git a/Framework/Kernel/inc/MantidKernel/WarningSuppressions.h b/Framework/Kernel/inc/MantidKernel/WarningSuppressions.h
index fb61f263ebbbc837021dbad04da2fb7a0dfb0548..0fb3dae2b43bda5b70c4a4e3a2c97ffb63151564 100644
--- a/Framework/Kernel/inc/MantidKernel/WarningSuppressions.h
+++ b/Framework/Kernel/inc/MantidKernel/WarningSuppressions.h
@@ -42,7 +42,15 @@
 
 // things to make the macros clearer
 #define GCC_DIAG_STR(s) #s
+// undefine definition from Poco 1.6
+#ifdef GCC_DIAG_JOINSTR
+#undef GCC_DIAG_JOINSTR
+#endif
 #define GCC_DIAG_JOINSTR(x, y) GCC_DIAG_STR(x##y)
+// undefine definition from Poco 1.6
+#ifdef GCC_DIAG_DO_PRAGMA
+#undef GCC_DIAG_DO_PRAGMA
+#endif
 #define GCC_DIAG_DO_PRAGMA(x) _Pragma(#x)
 #define GCC_DIAG_PRAGMA(x) GCC_DIAG_DO_PRAGMA(GCC diagnostic x)