diff --git a/src/libCom/osi/os/RTEMS/epicsMath.h b/src/libCom/osi/os/RTEMS/epicsMath.h
new file mode 100644
index 000000000..3b8b38f75
--- /dev/null
+++ b/src/libCom/osi/os/RTEMS/epicsMath.h
@@ -0,0 +1,25 @@
+/*************************************************************************\
+* Copyright (c) 2002 The University of Chicago, as Operator of Argonne
+*     National Laboratory.
+* Copyright (c) 2002 The Regents of the University of California, as
+*     Operator of Los Alamos National Laboratory.
+* EPICS BASE Versions 3.13.7
+* and higher are distributed subject to a Software License Agreement found
+* in file LICENSE that is included with this distribution. 
+\*************************************************************************/
+#ifndef epicsMathh
+#define epicsMathh
+
+#include <math.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int isnan(double);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* epicsMathh */