diff --git a/include/FLAC++/export.h b/include/FLAC++/export.h
index 62e5eff8..74a5299c 100644
--- a/include/FLAC++/export.h
+++ b/include/FLAC++/export.h
@@ -42,6 +42,9 @@
 #else
 #define FLACPP_API	_declspec(dllimport)
 
+/* every time the libFLAC++ API changes in any way, this number will be incremented */
+#define FLACPP_API_NUMBER 10
+
 #endif
 #endif
 #endif
diff --git a/include/FLAC/export.h b/include/FLAC/export.h
index 9ac92398..97802bb8 100644
--- a/include/FLAC/export.h
+++ b/include/FLAC/export.h
@@ -42,6 +42,9 @@
 #else
 #define FLAC_API	_declspec(dllimport)
 
+/* every time the libFLAC API changes in any way, this number will be incremented */
+#define FLAC_API_NUMBER 10
+
 #endif
 #endif
 #endif
diff --git a/include/OggFLAC++/export.h b/include/OggFLAC++/export.h
index a1eaa13c..88ab9064 100644
--- a/include/OggFLAC++/export.h
+++ b/include/OggFLAC++/export.h
@@ -42,6 +42,9 @@
 #else
 #define OggFLACPP_API	_declspec(dllimport)
 
+/* every time the libOggFLAC++ API changes in any way, this number will be incremented */
+#define OggFLACPP_API_NUMBER 10
+
 #endif
 #endif
 #endif
diff --git a/include/OggFLAC/export.h b/include/OggFLAC/export.h
index 858f2db9..14ef936c 100644
--- a/include/OggFLAC/export.h
+++ b/include/OggFLAC/export.h
@@ -42,6 +42,9 @@
 #else
 #define OggFLAC_API	_declspec(dllimport)
 
+/* every time the libOggFLAC API changes in any way, this number will be incremented */
+#define OggFLAC_API_NUMBER 10
+
 #endif
 #endif
 #endif