diff --git a/lib/Makefile.m32 b/lib/Makefile.m32
index bb01bbad3..3df923a72 100644
--- a/lib/Makefile.m32
+++ b/lib/Makefile.m32
@@ -106,6 +106,9 @@ endif
 ifeq ($(findstring -ares,$(CFG)),-ares)
 ARES = 1
 endif
+ifeq ($(findstring -sync,$(CFG)),-sync)
+SYNC = 1
+endif
 ifeq ($(findstring -rtmp,$(CFG)),-rtmp)
 RTMP = 1
 SSL = 1
@@ -151,11 +154,15 @@ endif
 INCLUDES = -I. -I../include
 CFLAGS += -DBUILDING_LIBCURL
 
-ifdef ARES
-  INCLUDES += -I"$(LIBCARES_PATH)"
-  CFLAGS += -DUSE_ARES -DCARES_STATICLIB
-  DLL_LIBS += -L"$(LIBCARES_PATH)" -lcares
-  libcurl_dll_DEPENDENCIES = $(LIBCARES_PATH)/libcares.a
+ifdef SYNC
+  CFLAGS += -DUSE_SYNC_DNS
+else
+  ifdef ARES
+    INCLUDES += -I"$(LIBCARES_PATH)"
+    CFLAGS += -DUSE_ARES -DCARES_STATICLIB
+    DLL_LIBS += -L"$(LIBCARES_PATH)" -lcares
+    libcurl_dll_DEPENDENCIES = $(LIBCARES_PATH)/libcares.a
+  endif
 endif
 ifdef RTMP
   INCLUDES += -I"$(LIBRTMP_PATH)"
diff --git a/lib/config-win32.h b/lib/config-win32.h
index c1e69541e..9ce6ad298 100644
--- a/lib/config-win32.h
+++ b/lib/config-win32.h
@@ -611,11 +611,10 @@
 /* Define to enable c-ares asynchronous DNS lookups. */
 /* #define USE_ARES 1 */
 
-/* Define to enable threaded asynchronous DNS lookups. */
-#if !defined(USE_ARES) && !defined(USE_THREADS_WIN32)
+/* Default define to enable threaded asynchronous DNS lookups. */
+#if !defined(USE_SYNC_DNS) && !defined(USE_ARES) && \
+    !defined(USE_THREADS_WIN32)
 #  define USE_THREADS_WIN32 1
-#elif defined(USE_THREADS_WIN32) && USE_THREADS_WIN32 == 0
-#  undef USE_THREADS_WIN32
 #endif
 
 #if defined(USE_ARES) && defined(USE_THREADS_WIN32)
diff --git a/src/Makefile.m32 b/src/Makefile.m32
index b8a60af2a..3dd7bd6b8 100644
--- a/src/Makefile.m32
+++ b/src/Makefile.m32
@@ -120,6 +120,9 @@ endif
 ifeq ($(findstring -ares,$(CFG)),-ares)
 ARES = 1
 endif
+ifeq ($(findstring -sync,$(CFG)),-sync)
+SYNC = 1
+endif
 ifeq ($(findstring -rtmp,$(CFG)),-rtmp)
 RTMP = 1
 SSL = 1
@@ -173,12 +176,16 @@ else
   CFLAGS += -DCURL_STATICLIB
   LDFLAGS += -static
 endif
-ifdef ARES
-  ifndef DYN
-    curl_DEPENDENCIES += $(LIBCARES_PATH)/libcares.a
+ifdef SYNC
+  CFLAGS += -DUSE_SYNC_DNS
+else
+  ifdef ARES
+    ifndef DYN
+      curl_DEPENDENCIES += $(LIBCARES_PATH)/libcares.a
+    endif
+    CFLAGS += -DUSE_ARES -DCARES_STATICLIB
+    curl_LDADD += -L"$(LIBCARES_PATH)" -lcares
   endif
-  CFLAGS += -DUSE_ARES -DCARES_STATICLIB
-  curl_LDADD += -L"$(LIBCARES_PATH)" -lcares
 endif
 ifdef RTMP
   CFLAGS += -DUSE_LIBRTMP