--- a/makedefs
+++ b/makedefs
@@ -500,7 +500,12 @@ EOF
 		: ${SHLIB_ENV="LD_LIBRARY_PATH=`pwd`/lib"}
 		: ${PLUGIN_LD="${CC-gcc} -shared"}
 		;;
-    Linux.3*)	SYSTYPE=LINUX3
+    Linux.[34]*)
+		case "$RELEASE" in
+		 3.*) SYSTYPE=LINUX3;;
+		 4.*) SYSTYPE=LINUX4;;
+		 *) error "Unknown Linux version: `uname -r`.";;
+		esac
 		case "$CCARGS" in
 		 *-DNO_DB*) ;;
 		 *-DHAS_DB*) ;;
--- a/src/util/sys_defs.h
+++ b/src/util/sys_defs.h
@@ -756,7 +756,7 @@ extern int initgroups(const char *, int);
  /*
   * LINUX.
   */
-#if defined(LINUX2) || defined(LINUX3)
+#if defined(LINUX2) || defined(LINUX3) || defined(LINUX4)
 #define SUPPORTED
 #include <sys/types.h>
 #define UINT32_TYPE	unsigned int