diff --git a/doc/cg.doc b/doc/cg.doc
index 32ff45fe..342fe8d0 100644
--- a/doc/cg.doc
+++ b/doc/cg.doc
@@ -1121,7 +1121,7 @@ Example mach.h for the PDP-11
 
 #define cst_fmt		"$%d."
 #define off_fmt		"%d."
-#define ilb_fmt		"I%02x%x"
+#define ilb_fmt		"I%x_%x"
 #define dlb_fmt		"_%d"
 #define	hol_fmt		"hol%d"
 
diff --git a/doc/ncg.doc b/doc/ncg.doc
index 16614b87..a470d242 100644
--- a/doc/ncg.doc
+++ b/doc/ncg.doc
@@ -2097,7 +2097,7 @@ Example mach.h for the PDP-11
 
 #define cst_fmt	"$%d."
 #define off_fmt	"%d."
-#define ilb_fmt	"I%02x%x"
+#define ilb_fmt	"I%x_%x"
 #define dlb_fmt	"_%d"
 #define hol_fmt	"hol%d"