diff --git a/lib/isc/include/isc/platform.h.in b/lib/isc/include/isc/platform.h.in
index 5bf8ccc214..73dbe80836 100644
--- a/lib/isc/include/isc/platform.h.in
+++ b/lib/isc/include/isc/platform.h.in
@@ -18,12 +18,6 @@
  ***** Platform-dependent defines.
  *****/
 
-/***
- *** Default strerror_r buffer size
- ***/
-
-#define ISC_STRERRORSIZE 128
-
 /***
  *** System limitations
  ***/
diff --git a/lib/isc/include/isc/strerr.h b/lib/isc/include/isc/strerr.h
index eebba51014..f2895986c2 100644
--- a/lib/isc/include/isc/strerr.h
+++ b/lib/isc/include/isc/strerr.h
@@ -15,6 +15,12 @@
 
 #include <isc/string.h>
 
+/***
+ *** Default strerror_r buffer size
+ ***/
+
+#define ISC_STRERRORSIZE 128
+
 #if defined(strerror_r)
 #undef strerror_r
 #endif /* if defined(strerror_r) */