diff --git a/mach/6500/libem/head_em.s b/mach/6500/libem/head_em.s
index 9cdfbb8a7..614e09ea7 100644
--- a/mach/6500/libem/head_em.s
+++ b/mach/6500/libem/head_em.s
@@ -8,6 +8,7 @@
 .define Ytmp, EXG, ARTH, RETURN, SIGN
 .define RETSIZE, TRAPVAL, STACK, BRANCH
 .define start, Push, Pop, STACKTh, STACKTl
+.define F_DUM
 
 ! DEFINITIONS
 
@@ -21,6 +22,8 @@ RDCH	= 0FFE0h	! This subroutine returns a character in
 OSBYTE	= 0FFF4h	! This subroutine performs miscelaneous
 			! operating system calls
 
+F_DUM	= 0		! Dummy floating point constant
+
 	! Here are the error numbers
 
 Earray	= 0