--- /dev/null
+--- postfix-3.3.7/makedefs~ 2020-02-08 13:42:07.000000000 +0100
++++ postfix-3.3.7/makedefs 2020-02-08 13:42:53.604246413 +0100
+@@ -546,7 +546,7 @@ EOF
+ : ${SHLIB_ENV="LD_LIBRARY_PATH=`pwd`/lib"}
+ : ${PLUGIN_LD="${CC-gcc} -shared"}
+ ;;
+- Linux.[34].*) SYSTYPE=LINUX$RELEASE_MAJOR
++ Linux.[3456].*) SYSTYPE=LINUX$RELEASE_MAJOR
+ case "$CCARGS" in
+ *-DNO_DB*) ;;
+ *-DHAS_DB*) ;;
+--- postfix-3.3.7/src/util/sys_defs.h~ 2020-02-08 13:43:34.000000000 +0100
++++ postfix-3.3.7/src/util/sys_defs.h 2020-02-08 13:44:42.064282215 +0100
+@@ -748,7 +748,7 @@ extern int initgroups(const char *, int)
+ /*
+ * LINUX.
+ */
+-#if defined(LINUX2) || defined(LINUX3) || defined(LINUX4)
++#if defined(LINUX2) || defined(LINUX3) || defined(LINUX4) || defined(LINUX5) || defined(LINUX6)
+ #define SUPPORTED
+ #define UINT32_TYPE unsigned int
+ #define UINT16_TYPE unsigned short