diff --git a/SWIG/Examples/test-suite/li_cstring.i b/SWIG/Examples/test-suite/li_cstring.i
index 274cee1be..fd92ac7d3 100644
--- a/SWIG/Examples/test-suite/li_cstring.i
+++ b/SWIG/Examples/test-suite/li_cstring.i
@@ -2,7 +2,7 @@
 
 %include "cstring.i"
 
-#ifndef _CSTRING_UNIMPL
+#ifndef SWIG_CSTRING_UNIMPL
 
 %cstring_input_binary(char *in, int n);
 %cstring_bounded_output(char *out1, 512);
diff --git a/SWIG/Examples/test-suite/li_cwstring.i b/SWIG/Examples/test-suite/li_cwstring.i
index a0d16ac09..dc9a1c4b9 100644
--- a/SWIG/Examples/test-suite/li_cwstring.i
+++ b/SWIG/Examples/test-suite/li_cwstring.i
@@ -2,7 +2,7 @@
 
 %include "cwstring.i"
 
-#ifndef _CSTRING_UNIMPL
+#ifndef SWIG_CWSTRING_UNIMPL
 
 %cwstring_input_binary(wchar_t *in, int n);
 %cwstring_bounded_output(wchar_t *out1, 512);
diff --git a/SWIG/Lib/cstring.i b/SWIG/Lib/cstring.i
index 510fffd67..27a25e01f 100644
--- a/SWIG/Lib/cstring.i
+++ b/SWIG/Lib/cstring.i
@@ -1,6 +1,8 @@
 %echo "cstring.i not implemented for this target"
+#define SWIG_CSTRING_UNIMPL
 
-#define _CSTRING_UNIMPL
+/* old name keep for compatibility */
+#define _CSTRING_UNIMPL