diff --git a/src/tools/vppapigen/vppapigen.py b/src/tools/vppapigen/vppapigen.py
index ce05cbe..2b0ce99 100755
--- a/src/tools/vppapigen/vppapigen.py
+++ b/src/tools/vppapigen/vppapigen.py
@@ -752,6 +752,7 @@
         """define : DEFINE ID '{' block_statements_opt '}' ';'"""
         self.fields = []
         p[0] = Define(p[2], [], p[4], self.last_comment)
+        self.last_comment = None
 
     def p_define_flist(self, p):
         """define : flist DEFINE ID '{' block_statements_opt '}' ';'"""
@@ -763,6 +764,7 @@
             )
         else:
             p[0] = Define(p[3], p[1], p[5], self.last_comment)
+            self.last_comment = None
 
     def p_flist(self, p):
         """flist : flag
diff --git a/src/tools/vppapigen/vppapigen_json.py b/src/tools/vppapigen/vppapigen_json.py
index ba32e28..0a1a3d3 100644
--- a/src/tools/vppapigen/vppapigen_json.py
+++ b/src/tools/vppapigen/vppapigen_json.py
@@ -77,7 +77,8 @@
             c = {}
             c["crc"] = "{0:#0{1}x}".format(t.crc, 10)
             c["options"] = t.options
-            c["comment"] = t.comment
+            if t.comment:
+                c["comment"] = t.comment
             d.append(c)
 
         r.append(d)