diff --git a/m4/ax_harden_compiler_flags.m4 b/m4/ax_harden_compiler_flags.m4
index c02af319d..adcbebfb4 100644
--- a/m4/ax_harden_compiler_flags.m4
+++ b/m4/ax_harden_compiler_flags.m4
@@ -117,7 +117,7 @@
       AX_APPEND_COMPILE_FLAGS([-Wno-pragmas],,[$ax_append_compile_cflags_extra])
 
       AX_APPEND_COMPILE_FLAGS([-Wall],,[$ax_append_compile_cflags_extra])
-      AX_APPEND_COMPILE_FLAGS([-Wno-strict-aliasing],,,[$ax_append_compile_cflags_extra])
+      AX_APPEND_COMPILE_FLAGS([-Wno-strict-aliasing],,[$ax_append_compile_cflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wextra],,[$ax_append_compile_cflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wunknown-pragmas],,[$ax_append_compile_cflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wthis-test-should-fail],,[$ax_append_compile_cflags_extra])
@@ -186,7 +186,7 @@
         ])
 
       AX_APPEND_COMPILE_FLAGS([-Wall],,[$ax_append_compile_cxxflags_extra])
-      AX_APPEND_COMPILE_FLAGS([-Wno-strict-aliasing],,,[$ax_append_compile_cxxflags_extra])
+      AX_APPEND_COMPILE_FLAGS([-Wno-strict-aliasing],,[$ax_append_compile_cxxflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wextra],,[$ax_append_compile_cxxflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wunknown-pragmas],,[$ax_append_compile_cxxflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wthis-test-should-fail],,[$ax_append_compile_cxxflags_extra])