diff --git a/nc_optimisation.cmake b/nc_optimisation.cmake
index 4bd5632..14e2cc9 100644
--- a/nc_optimisation.cmake
+++ b/nc_optimisation.cmake
@@ -65,9 +65,25 @@ canonical_host()
 
 ##-----------------------------------------------------------------------------
 if (${host_cpu} STREQUAL "x86_64")
+    # Explicitly qualify the CPU as the minimum viable architecture, but tune
+    # for common platforms. This might prevent some invalid instructions being
+    # emitted.
+    append_compile_flag(-march=x86-64)
     append_compile_flag(-mtune=generic)
-    append_compile_flag(-msse3)
-    append_compile_flag(-msahf)
+
+    append_compile_flag(-msse)
+    append_compile_flag(-msse2)
+    append_compile_flag(-mno-sse3)
+    append_compile_flag(-mssse3)
+    append_compile_flag(-mno-avx)
+    append_compile_flag(-mno-avx2)
+
+    # These instructions should always be available on reasonable platforms.
+    # They're almost 20 years old at this point.
+    #append_compile_flag(-msse)
+    #append_compile_flag(-msse2)
+    # append_compile_flag(-mssse3)
+    # append_compile_flag(-msahf)
 elseif (${host_cpu} STREQUAL "i686")
     append_compile_flag(-march=prescott)
     append_compile_flag(-mtune=generic)