diff --git a/m4/ax_linuxkm.m4 b/m4/ax_linuxkm.m4
index 5bfa362ee..60ffbe8d0 100644
--- a/m4/ax_linuxkm.m4
+++ b/m4/ax_linuxkm.m4
@@ -56,24 +56,23 @@ AC_DEFUN([AX_SIMD_CC_COMPILER_FLAGS], [
 
     AC_LANG_PUSH([C])
 
-    if test -z "$CFLAGS_FPU_DISABLE"; then
+    if test "$CFLAGS_FPU_DISABLE" = ""; then
         AX_APPEND_COMPILE_FLAGS([-mno-80387],[CFLAGS_FPU_DISABLE])
         AX_APPEND_COMPILE_FLAGS([-mno-fp-ret-in-387],[CFLAGS_FPU_DISABLE])
         AX_APPEND_COMPILE_FLAGS([-mno-fpu],[CFLAGS_FPU_DISABLE])
     fi
 
-    if test -z "$CFLAGS_FPU_ENABLE"; then
+    if test "$CFLAGS_FPU_ENABLE" = ""; then
         AX_APPEND_COMPILE_FLAGS([-m80387],[CFLAGS_FPU_ENABLE])
         AX_APPEND_COMPILE_FLAGS([-mfpu],[CFLAGS_FPU_ENABLE])
     fi
 
-    if test -z "$CFLAGS_SIMD_DISABLE"; then
+    if test "$CFLAGS_SIMD_DISABLE" = ""; then
         AX_APPEND_COMPILE_FLAGS([-mno-sse],[CFLAGS_SIMD_DISABLE])
         AX_APPEND_COMPILE_FLAGS([-mgeneral-regs-only],[CFLAGS_SIMD_DISABLE])
-        AX_APPEND_COMPILE_FLAGS([-mno-sse],[CFLAGS_SIMD_DISABLE])
     fi
 
-    if test -z "$CFLAGS_SIMD_ENABLE"; then
+    if test "$CFLAGS_SIMD_ENABLE" = ""; then
         AX_APPEND_COMPILE_FLAGS([-msse],[CFLAGS_SIMD_ENABLE])
         AX_APPEND_COMPILE_FLAGS([-mmmx],[CFLAGS_SIMD_ENABLE])
         AX_APPEND_COMPILE_FLAGS([-msse2],[CFLAGS_SIMD_ENABLE])
@@ -83,14 +82,14 @@ AC_DEFUN([AX_SIMD_CC_COMPILER_FLAGS], [
         AX_APPEND_COMPILE_FLAGS([-mno-general-regs-only],[CFLAGS_SIMD_ENABLE])
     fi
 
-    if test -z "$CFLAGS_AUTO_VECTORIZE_DISABLE"; then
+    if test "$CFLAGS_AUTO_VECTORIZE_DISABLE" = ""; then
         AX_APPEND_COMPILE_FLAGS([-fno-builtin],[CFLAGS_AUTO_VECTORIZE_DISABLE])
         AX_APPEND_COMPILE_FLAGS([-fno-tree-vectorize],[CFLAGS_AUTO_VECTORIZE_DISABLE])
         AX_APPEND_COMPILE_FLAGS([-fno-tree-loop-vectorize],[CFLAGS_AUTO_VECTORIZE_DISABLE])
         AX_APPEND_COMPILE_FLAGS([-fno-tree-slp-vectorize],[CFLAGS_AUTO_VECTORIZE_DISABLE])
     fi
 
-    if test -z "$CFLAGS_AUTO_VECTORIZE_ENABLE"; then
+    if test "$CFLAGS_AUTO_VECTORIZE_ENABLE" = ""; then
         AX_APPEND_COMPILE_FLAGS([-fbuiltin],[CFLAGS_AUTO_VECTORIZE_ENABLE])
         AX_APPEND_COMPILE_FLAGS([-ftree-vectorize],[CFLAGS_AUTO_VECTORIZE_ENABLE])
         AX_APPEND_COMPILE_FLAGS([-ftree-loop-vectorize],[CFLAGS_AUTO_VECTORIZE_ENABLE])