diff --git a/gdbinit b/gdbinit
index 812f04b59..fdc9c759b 100644
--- a/gdbinit
+++ b/gdbinit
@@ -198,3 +198,7 @@ end
 define inst
   p scm_instruction_table[$arg0]
 end
+
+define gbt
+  call scm_display_backtrace (scm_make_stack(0x404,0x304), scm_current_error_port (), 0x704, 0x704, 0x704)
+end
diff --git a/module/system/vm/program.scm b/module/system/vm/program.scm
index 99f9a3cb9..31b667bb0 100644
--- a/module/system/vm/program.scm
+++ b/module/system/vm/program.scm
@@ -121,6 +121,7 @@
     (and arities
          (let lp ((arities arities))
            (cond ((null? arities) #f)
+                 ((not ip) (car arities)) ; take the first one
                  ((and (< (arity:start (car arities)) ip)
                        (<= ip (arity:end (car arities))))
                   (car arities))