diff --git a/Makefile.am b/Makefile.am
index 0f24ee6bd..2230e628f 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -37,15 +37,13 @@ DISTCLEANFILES += jimtcl/jsmn/jsmn.o
 endif
 
 # common flags used in openocd build
-AM_CFLAGS = $(GCC_WARNINGS)\
-			  -DFD_SETSIZE=128
+AM_CFLAGS = $(GCC_WARNINGS)
 
 AM_CPPFLAGS = $(HOST_CPPFLAGS)\
 			  -I$(top_srcdir)/src \
 			  -I$(top_builddir)/src \
 			  -DPKGDATADIR=\"$(pkgdatadir)\" \
-			  -DBINDIR=\"$(bindir)\"\
-			  -DFD_SETSIZE=128
+			  -DBINDIR=\"$(bindir)\"
 
 if INTERNAL_JIMTCL
 AM_CPPFLAGS += -I$(top_srcdir)/jimtcl \
diff --git a/configure.ac b/configure.ac
index f13727e89..779de40c6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -436,7 +436,7 @@ AS_CASE([$host],
     # In case enable_buspirate=auto, make sure it will not be built.
     enable_buspirate=no
 
-    AC_SUBST([HOST_CPPFLAGS], [-D__USE_MINGW_ANSI_STDIO])
+    AC_SUBST([HOST_CPPFLAGS], ["-D__USE_MINGW_ANSI_STDIO -DFD_SETSIZE=128"])
   ],
   [*darwin*], [
     is_darwin=yes