diff --git a/RELNOTES b/RELNOTES
index 8708c35f..3fd28355 100644
--- a/RELNOTES
+++ b/RELNOTES
@@ -202,6 +202,9 @@ work on other platforms. Please report any problems and suggested fixes to
   over-riding vlaues were not present in a matching fixed-address6 host
   configuration.
 
+- ./configure now checks to ensure the intX_t and u_intX_t types are defined,
+  correcting a compilation failure when using Sun's compiler.
+
 			Changes since 4.1.0b1
 
 - A missing "else" in dhcrelay.c could have caused an interface not to
diff --git a/configure.ac b/configure.ac
index e62c689b..1643f622 100644
--- a/configure.ac
+++ b/configure.ac
@@ -318,6 +318,28 @@ AC_ARG_WITH(relay-pid-file,
 	AC_DEFINE_UNQUOTED([_PATH_DHCRELAY_PID], ["$withval"],
 			   [File for dhcrelay process information.]))
 
+# Check basic types.
+AC_TYPE_INT8_T
+AC_TYPE_INT16_T
+AC_TYPE_INT32_T
+
+# Some systems need the u_intX_t types defined across.
+AC_CHECK_TYPE([u_int8_t], [], [
+  AC_TYPE_UINT8_T
+  AC_DEFINE(u_int8_t, [uint8_t], [Define a type for 8-bit unsigned
+				  integers.])
+])
+AC_CHECK_TYPE([u_int16_t], [], [
+  AC_TYPE_UINT16_T
+  AC_DEFINE(u_int16_t, [uint16_t], [Define a type for 16-bit unsigned
+				    integers.])
+])
+AC_CHECK_TYPE([u_int32_t], [], [
+  AC_TYPE_UINT32_T
+  AC_DEFINE(u_int32_t, [uint32_t], [Define a type for 32-bit unsigned
+				    integers.])
+])
+
 # see if ifaddrs.h is available
 AC_CHECK_HEADERS(ifaddrs.h)