diff --git a/Makefile.am b/Makefile.am
index b7d070eb..4cb10391 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -145,7 +145,7 @@ src_libespeak_ng_la_LDFLAGS = -version-info $(SHARED_VERSION) -lpthread -lm \
 src_libespeak_ng_la_CFLAGS = \
 	-fPIC -fvisibility=hidden \
 	-pedantic -fno-exceptions -DPATH_ESPEAK_DATA=\"$(DATADIR)\" -DLIBESPEAK_NG_EXPORT \
-	${PCAUDIOLIB_CFLAGS} ${AM_CFLAGS}
+	${PCAUDIOLIB_CFLAGS} ${SONIC_CFLAGS} ${AM_CFLAGS}
 
 src_libespeak_ng_la_SOURCES = \
 	src/ucd-tools/src/case.c \
diff --git a/configure.ac b/configure.ac
index ed5c97ff..1359545f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -221,7 +221,7 @@ else
     AC_CHECK_HEADERS([pcaudiolib/audio.h],
         [
             have_pcaudiolib=yes
-            PCAUDIOLIB_CFLAGS=
+            PCAUDIOLIB_CFLAGS=-DUSE_LIBPCAUDIO=1
             PCAUDIOLIB_LIBS=-lpcaudio
         ],[
             have_pcaudiolib=no
@@ -258,12 +258,14 @@ if test "$with_sonic" = "no" ; then
 else
     AC_CHECK_HEADERS([sonic.h],
         [
+            SONIC_CFLAGS=-DUSE_LIBSONIC=1
             AC_CHECK_LIB([sonic], [sonicCreateStream])
             have_sonic=yes
         ],[
             have_sonic=no
         ])
 fi
+AC_SUBST(SONIC_CFLAGS)
 
 AC_CHECK_HEADERS([valgrind/memcheck.h])
 
diff --git a/src/windows/libespeak-ng.vcxproj b/src/windows/libespeak-ng.vcxproj
index 1ea3935d..9c5979e9 100644
--- a/src/windows/libespeak-ng.vcxproj
+++ b/src/windows/libespeak-ng.vcxproj
@@ -88,7 +88,7 @@
       <WarningLevel>TurnOffAllWarnings</WarningLevel>
       <Optimization>Disabled</Optimization>
       <AdditionalIncludeDirectories>$(ProjectDir);$(ProjectDir)/../include;$(ProjectDir)/../pcaudiolib/src/include;$(ProjectDir)/../speechPlayer/include;$(ProjectDir)/../include/compat;$(ProjectDir)/../ucd-tools/src/include</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>LIBESPEAK_NG_EXPORT;INCLUDE_KLATT;INCLUDE_SPEECHPLAYER;INCLUDE_MBROLA;HAVE_PCAUDIOLIB_AUDIO_H;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>LIBESPEAK_NG_EXPORT;USE_KLATT=1;USE_SPEECHPLAYER=1;USE_MBROLA=1;USE_LIBPCAUDIO=1;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <ProgramDataBaseFileName>$(IntDir)libespeak-ng.pdb</ProgramDataBaseFileName>
     </ClCompile>
     <Link>
@@ -104,7 +104,7 @@
       </PrecompiledHeader>
       <WarningLevel>TurnOffAllWarnings</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <PreprocessorDefinitions>LIBESPEAK_NG_EXPORT;INCLUDE_KLATT;INCLUDE_SPEECHPLAYER;INCLUDE_MBROLA;HAVE_PCAUDIOLIB_AUDIO_H;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>LIBESPEAK_NG_EXPORT;USE_KLATT=1;USE_SPEECHPLAYER=1;USE_MBROLA=1;USE_LIBPCAUDIO=1;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <ProgramDataBaseFileName>$(IntDir)libespeak-ng.pdb</ProgramDataBaseFileName>
       <AdditionalIncludeDirectories>$(ProjectDir);$(ProjectDir)/../include;$(ProjectDir)/../pcaudiolib/src/include;$(ProjectDir)/../speechPlayer/include;$(ProjectDir)/../include/compat;$(ProjectDir)/../ucd-tools/src/include</AdditionalIncludeDirectories>
     </ClCompile>
@@ -124,7 +124,7 @@
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <AdditionalIncludeDirectories>$(ProjectDir);$(ProjectDir)/../include;$(ProjectDir)/../pcaudiolib/src/include;$(ProjectDir)/../speechPlayer/include;$(ProjectDir)/../include/compat;$(ProjectDir)/../ucd-tools/src/include</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>LIBESPEAK_NG_EXPORT;INCLUDE_KLATT;INCLUDE_SPEECHPLAYER;INCLUDE_MBROLA;HAVE_PCAUDIOLIB_AUDIO_H;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>LIBESPEAK_NG_EXPORT;USE_KLATT=1;USE_SPEECHPLAYER=1;USE_MBROLA=1;USE_LIBPCAUDIO=1;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <ProgramDataBaseFileName>$(IntDir)libespeak-ng.pdb</ProgramDataBaseFileName>
     </ClCompile>
     <Link>
@@ -144,7 +144,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>LIBESPEAK_NG_EXPORT;INCLUDE_KLATT;INCLUDE_SPEECHPLAYER;INCLUDE_MBROLA;HAVE_PCAUDIOLIB_AUDIO_H;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>LIBESPEAK_NG_EXPORT;USE_KLATT=1;USE_SPEECHPLAYER=1;USE_MBROLA=1;USE_LIBPCAUDIO=1;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <ProgramDataBaseFileName>$(IntDir)libespeak-ng.pdb</ProgramDataBaseFileName>
       <AdditionalIncludeDirectories>$(ProjectDir);$(ProjectDir)/../include;$(ProjectDir)/../pcaudiolib/src/include;$(ProjectDir)/../speechPlayer/include;$(ProjectDir)/../include/compat;$(ProjectDir)/../ucd-tools/src/include</AdditionalIncludeDirectories>
     </ClCompile>