diff --git a/src/libCom/osi/epicsMath.cpp b/src/libCom/osi/epicsMath.cpp
index 8628d61e9..c0e9d9068 100644
--- a/src/libCom/osi/epicsMath.cpp
+++ b/src/libCom/osi/epicsMath.cpp
@@ -21,5 +21,7 @@ static float makeINF ( void )
     return a / b;
 }
 
+extern "C" {
 epicsShareDef float epicsNAN = makeNAN();
 epicsShareDef float epicsINF = makeINF();
+}