diff --git a/dlib/simd/simd_check.h b/dlib/simd/simd_check.h
index 9f2df441a..9d36e0e7b 100644
--- a/dlib/simd/simd_check.h
+++ b/dlib/simd/simd_check.h
@@ -91,7 +91,6 @@
 #ifdef DLIB_HAVE_SSE2
     #include <xmmintrin.h>
     #include <emmintrin.h>
-    #include <mmintrin.h>
 #endif
 #ifdef DLIB_HAVE_SSE3
     #include <pmmintrin.h> // SSE3