diff --git a/lib/asn1/gen.c b/lib/asn1/gen.c
index 35de799d9..55ec5f647 100644
--- a/lib/asn1/gen.c
+++ b/lib/asn1/gen.c
@@ -1925,10 +1925,13 @@ generate_type_header (const Symbol *s)
      * member fields are not OPTIONAL/DEFAULTed.
      */
     generate_subtypes_header(s);
-    fprintf(headerfile, "/*\n");
-    fprintf(headerfile, "%s ::= ", s->name);
-    define_asn1 (0, s->type);
-    fprintf(headerfile, "\n*/\n\n");
+    if (!s->emitted_asn1) {
+        fprintf(headerfile, "/*\n");
+        fprintf(headerfile, "%s ::= ", s->name);
+        define_asn1 (0, s->type);
+        fprintf(headerfile, "\n*/\n\n");
+        emitted_asn1(s);
+    }
 
     /*
      * Emit enums for the outermost tag of this type.  These are needed for
diff --git a/lib/asn1/symbol.c b/lib/asn1/symbol.c
index 920ed16f7..b472ebd28 100644
--- a/lib/asn1/symbol.c
+++ b/lib/asn1/symbol.c
@@ -171,3 +171,9 @@ emitted_tag_enums(const Symbol *s)
 {
     ((Symbol *)(uintptr_t)s)->emitted_tag_enums = 1;
 }
+
+void
+emitted_asn1(const Symbol *s)
+{
+    ((Symbol *)(uintptr_t)s)->emitted_asn1 = 1;
+}
diff --git a/lib/asn1/symbol.h b/lib/asn1/symbol.h
index bce2e1fe4..108749b92 100644
--- a/lib/asn1/symbol.h
+++ b/lib/asn1/symbol.h
@@ -238,6 +238,7 @@ struct symbol {
     IOSObject *object;
     IOSObjectSet *objectset;
     HEIM_TAILQ_ENTRY(symbol) symlist;
+    unsigned int emitted_asn1:1;
     unsigned int emitted_declaration:1;
     unsigned int emitted_definition:1;
     unsigned int emitted_tag_enums:1;
@@ -260,6 +261,7 @@ Symbol *getsym(char *name);
 void output_name (char *);
 int checkundefined(void);
 void generate_types(void);
+void emitted_asn1(const Symbol *);
 void emitted_declaration(const Symbol *);
 void emitted_definition(const Symbol *);
 void emitted_tag_enums(const Symbol *);