diff --git a/src/include/os/alpha/osiSock.h b/src/include/os/alpha/osiSock.h
index 4740f19a6..4b9895cfc 100644
--- a/src/include/os/alpha/osiSock.h
+++ b/src/include/os/alpha/osiSock.h
@@ -8,6 +8,7 @@
 
 #ifdef __cplusplus
 extern "C" {
+struct ifafilt;
 #endif
 
 #include <errno.h>
diff --git a/src/libCom/osi/os/alpha/osdSock.h b/src/libCom/osi/os/alpha/osdSock.h
index 4740f19a6..4b9895cfc 100644
--- a/src/libCom/osi/os/alpha/osdSock.h
+++ b/src/libCom/osi/os/alpha/osdSock.h
@@ -8,6 +8,7 @@
 
 #ifdef __cplusplus
 extern "C" {
+struct ifafilt;
 #endif
 
 #include <errno.h>