diff --git a/src/vim9compile.c b/src/vim9compile.c
index a70ed5a..a6b4ba4 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -2593,6 +2593,9 @@
 	// The return type will now be known.
 	set_function_type(ufunc);
 
+	// The function reference count will be 1.  When the ISN_FUNCREF
+	// instruction is deleted the reference count is decremented and the
+	// function is freed.
 	return generate_FUNCREF(cctx, ufunc);
     }
 
@@ -7424,6 +7427,18 @@
     }
 }
 
+/*
+ * Used when a user function is about to be deleted: remove the pointer to it.
+ * The entry in def_functions is then unused.
+ */
+    void
+unlink_def_function(ufunc_T *ufunc)
+{
+    dfunc_T *dfunc = ((dfunc_T *)def_functions.ga_data) + ufunc->uf_dfunc_idx;
+
+    dfunc->df_ufunc = NULL;
+}
+
 #if defined(EXITFREE) || defined(PROTO)
 /*
  * Free all functions defined with ":def".