diff --git a/simon-simd.cpp b/simon-simd.cpp
index da9c5e9a..ea9c3f90 100644
--- a/simon-simd.cpp
+++ b/simon-simd.cpp
@@ -40,6 +40,8 @@
 // https://www.spinics.net/lists/gcchelp/msg47749.html
 #if (CRYPTOPP_GCC_VERSION >= 40900)
 # define GCC_NO_UBSAN __attribute__ ((no_sanitize_undefined))
+#else
+# define GCC_NO_UBSAN
 #endif
 
 ANONYMOUS_NAMESPACE_BEGIN
diff --git a/speck-simd.cpp b/speck-simd.cpp
index 6ac1687a..3ffcbb28 100644
--- a/speck-simd.cpp
+++ b/speck-simd.cpp
@@ -49,6 +49,8 @@
 // https://www.spinics.net/lists/gcchelp/msg47749.html
 #if (CRYPTOPP_GCC_VERSION >= 40900)
 # define GCC_NO_UBSAN __attribute__ ((no_sanitize_undefined))
+#else
+# define GCC_NO_UBSAN
 #endif
 
 ANONYMOUS_NAMESPACE_BEGIN