diff --git a/src/libCom/osi/os/RTEMS/epicsMath.h b/src/libCom/osi/os/RTEMS/epicsMath.h
index 848b375ee..be7005b6b 100644
--- a/src/libCom/osi/os/RTEMS/epicsMath.h
+++ b/src/libCom/osi/os/RTEMS/epicsMath.h
@@ -11,5 +11,6 @@
 #define epicsMathh
 
 #include <math.h>
+#include <ieeefp.h>
 
 #endif /* epicsMathh */