diff --git a/Makefile.am b/Makefile.am
index ddeb3efd..595a5aea 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -45,10 +45,12 @@ libuv_la_SOURCES = src/fs-poll.c \
                    src/version.c
 
 if SUNOS
+if GCC
 # Can't be turned into a CC_CHECK_CFLAGS in configure.ac, it makes compilers
 # on other platforms complain that the argument is unused during compilation.
 libuv_la_CFLAGS += -pthreads
 endif
+endif
 
 if WINNT
 
@@ -141,14 +143,20 @@ check_PROGRAMS = test/run-tests
 if OS390
 test_run_tests_CFLAGS =
 else
+if GCC
 test_run_tests_CFLAGS = -Wno-long-long
+else
+test_run_tests_CFLAGS =
+endif
 endif
 
 if SUNOS
+if GCC
 # Can't be turned into a CC_CHECK_CFLAGS in configure.ac, it makes compilers
 # on other platforms complain that the argument is unused during compilation.
 test_run_tests_CFLAGS += -pthreads
 endif
+endif
 
 test_run_tests_LDFLAGS =
 test_run_tests_SOURCES = test/blackhole-server.c \
@@ -324,7 +332,9 @@ test_run_tests_CFLAGS += -D_GNU_SOURCE
 endif
 
 if SUNOS
-test_run_tests_CFLAGS += -D__EXTENSIONS__ -D_XOPEN_SOURCE=500
+test_run_tests_CFLAGS += -D__EXTENSIONS__ \
+                         -D_XOPEN_SOURCE=500 \
+                         -D_REENTRANT
 endif
 
 if OS390
@@ -462,7 +472,9 @@ endif
 
 if SUNOS
 uvinclude_HEADERS += include/uv/sunos.h
-libuv_la_CFLAGS += -D__EXTENSIONS__ -D_XOPEN_SOURCE=500
+libuv_la_CFLAGS += -D__EXTENSIONS__ \
+                   -D_XOPEN_SOURCE=500 \
+                   -D_REENTRANT
 libuv_la_SOURCES += src/unix/no-proctitle.c \
                     src/unix/sunos.c
 endif
diff --git a/configure.ac b/configure.ac
index 931ac3e3..fb1b0acd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -24,16 +24,18 @@ AC_ENABLE_SHARED
 AC_ENABLE_STATIC
 AC_PROG_CC
 AM_PROG_CC_C_O
-AS_IF([AS_CASE([$host_os],[openedition*],  [false], [true])], [
-  CC_CHECK_CFLAGS_APPEND([-pedantic])
-])
 CC_FLAG_VISIBILITY #[-fvisibility=hidden]
 CC_CHECK_CFLAGS_APPEND([-g])
-CC_CHECK_CFLAGS_APPEND([-std=gnu89])
-CC_CHECK_CFLAGS_APPEND([-Wall])
-CC_CHECK_CFLAGS_APPEND([-Wextra])
-CC_CHECK_CFLAGS_APPEND([-Wno-unused-parameter])
-CC_CHECK_CFLAGS_APPEND([-Wstrict-prototypes])
+AS_IF([test "x$GCC" = xyes], [
+  AS_IF([AS_CASE([$host_os], [openedition*], [false], [true])], [
+    CC_CHECK_CFLAGS_APPEND([-pedantic])
+  ])
+  CC_CHECK_CFLAGS_APPEND([-std=gnu89])
+  CC_CHECK_CFLAGS_APPEND([-Wall])
+  CC_CHECK_CFLAGS_APPEND([-Wextra])
+  CC_CHECK_CFLAGS_APPEND([-Wno-unused-parameter])
+  CC_CHECK_CFLAGS_APPEND([-Wstrict-prototypes])
+])
 # AM_PROG_AR is not available in automake v0.11 but it's essential in v0.12.
 m4_ifdef([AM_PROG_AR], [AM_PROG_AR])
 # autoconf complains if AC_PROG_LIBTOOL precedes AM_PROG_AR.
@@ -50,6 +52,7 @@ AC_CHECK_LIB([rt], [clock_gettime])
 AC_CHECK_LIB([sendfile], [sendfile])
 AC_CHECK_LIB([socket], [socket])
 AC_SYS_LARGEFILE
+AM_CONDITIONAL([GCC],      [AS_IF([test "x$GCC" = xyes],        [true], [false])])
 AM_CONDITIONAL([AIX],      [AS_CASE([$host_os],[aix*],          [true], [false])])
 AM_CONDITIONAL([ANDROID],  [AS_CASE([$host_os],[linux-android*],[true], [false])])
 AM_CONDITIONAL([CYGWIN],   [AS_CASE([$host_os],[cygwin*],       [true], [false])])