diff --git a/GNUmakefile b/GNUmakefile
index 6267391d..16f132de 100755
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -249,6 +249,8 @@ ifeq ($(findstring -DCRYPTOPP_DISABLE_SSE4,$(CXXFLAGS)),)
   HAVE_SSE4 = $(shell echo | $(CXX) -x c++ $(CXXFLAGS) -msse4.1 -dM -E - 2>/dev/null | $(GREP) -i -c __SSE4_1__)
   ifeq ($(HAVE_SSE4),1)
     BLAKE2_FLAG = -msse4.1
+    SIMON_FLAG = -msse4.1
+    SPECK_FLAG = -msse4.1
   endif
   HAVE_SSE4 = $(shell echo | $(CXX) -x c++ $(CXXFLAGS) -msse4.2 -dM -E - 2>/dev/null | $(GREP) -i -c __SSE4_2__)
   ifeq ($(HAVE_SSE4),1)