diff --git a/configure.ac b/configure.ac
index fc64be16e..ef71edf57 100644
--- a/configure.ac
+++ b/configure.ac
@@ -72,7 +72,7 @@ AC_CHECK_HEADERS(unistd.h sys/mman.h)
 
 # Compiler flags
 AC_CANONICAL_HOST
-AC_CHECK_ALIGNOF([struct{char}])
+AC_CHECK_ALIGNOF([struct{char;}])
 if test "x$GCC" = "xyes"; then
 
 	# Make symbols link locally
@@ -95,7 +95,7 @@ if test "x$GCC" = "xyes"; then
 
 	case "$host" in
 		arm-*-*)
-			if test "x$ac_cv_alignof_struct_char_" != x1; then
+			if test "x$ac_cv_alignof_struct_char__" != x1; then
 				# Request byte alignment
 				CXXFLAGS="$CXXFLAGS -mstructure-size-boundary=8"
 			fi