diff --git a/src/cc65/declare.c b/src/cc65/declare.c
index ac58948bf..636e0d61d 100644
--- a/src/cc65/declare.c
+++ b/src/cc65/declare.c
@@ -919,6 +919,11 @@ NextMember: if (CurTok.Tok != TOK_COMMA) {
     FieldTab = GetSymTab ();
     LeaveStructLevel ();
 
+    /* Empty union is not supported now */
+    if (UnionSize == 0) {
+        Error ("Empty union type '%s' is not supported", Name);
+    }
+
     /* Make a real entry from the forward decl and return it */
     return AddStructSym (Name, SC_UNION | SC_DEF, UnionSize, FieldTab);
 }
@@ -1101,6 +1106,11 @@ NextMember: if (CurTok.Tok != TOK_COMMA) {
     FieldTab = GetSymTab ();
     LeaveStructLevel ();
 
+    /* Empty struct is not supported now */
+    if (StructSize == 0) {
+        Error ("Empty struct type '%s' is not supported", Name);
+    }
+
     /* Make a real entry from the forward decl and return it */
     return AddStructSym (Name, SC_STRUCT | SC_DEF, StructSize, FieldTab);
 }