diff --git a/acinclude.m4.in b/acinclude.m4.in
index 3d4bd86..de797c1 100644
--- a/acinclude.m4.in
+++ b/acinclude.m4.in
@@ -3568,7 +3568,7 @@ AC_DEFUN([AC_CHECK_COMPILERS],
         CXXFLAGS="-Wall -W -Wpointer-arith $CXXFLAGS"
         case $host in
           *-*-linux-gnu)	
-            CFLAGS="-std=iso9899:1990 -W -Wall -Wchar-subscripts -Wshadow -Wpointer-arith -Wmissing-prototypes -Wwrite-strings -D_XOPEN_SOURCE=500 -D_BSD_SOURCE $CFLAGS"
+            CFLAGS="-std=iso9899:1999 -W -Wall -Wchar-subscripts -Wshadow -Wpointer-arith -Wmissing-prototypes -Wwrite-strings -D_XOPEN_SOURCE=500 -D_BSD_SOURCE $CFLAGS"
             CXXFLAGS="-ansi -D_XOPEN_SOURCE=500 -D_BSD_SOURCE -Wcast-align -Wchar-subscripts $CXXFLAGS"
             KDE_CHECK_COMPILER_FLAG(Wmissing-format-attribute, [CXXFLAGS="$CXXFLAGS -Wformat-security -Wmissing-format-attribute"])
             KDE_CHECK_C_COMPILER_FLAG(Wmissing-format-attribute, [CFLAGS="$CFLAGS -Wformat-security -Wmissing-format-attribute"])