diff --git a/src/data.cpp b/src/data.cpp
index bf32579..019a3fd 100644
--- a/src/data.cpp
+++ b/src/data.cpp
@@ -969,10 +969,11 @@ size_t Value::nmembers() const
 {
     switch(desc ? desc->code.code : TypeCode::Null) {
     case TypeCode::Struct:
-    case TypeCode::StructA:
     case TypeCode::Union:
-    case TypeCode::UnionA:
         return desc->miter.size();
+    case TypeCode::StructA:
+    case TypeCode::UnionA:
+        return desc->members[0].miter.size();
     default:
         return 0u;
     }
diff --git a/src/dataimpl.h b/src/dataimpl.h
index bf09401..dd5adf8 100644
--- a/src/dataimpl.h
+++ b/src/dataimpl.h
@@ -72,7 +72,7 @@ struct FieldDesc {
     size_t parent_index=0;
 
     // For Union, UnionA, StructA
-    // For Union, the choices concatenated together (members.size() !+ #choices)
+    // For Union, the choices concatenated together (members.size() != #choices)
     // For UnionA/StructA containing a single Union/Struct
     std::vector<FieldDesc> members;
 
diff --git a/src/pvxs/data.h b/src/pvxs/data.h
index 850d52a..94eb40b 100644
--- a/src/pvxs/data.h
+++ b/src/pvxs/data.h
@@ -741,6 +741,7 @@ public:
 
     //! Number of child fields.
     //! only Struct, StructA, Union, UnionA return non-zero
+    //! \since UNRELEASED correctly return non-zero for StructA and UnionA
     size_t nmembers() const;
 
     struct _IAll {};
diff --git a/test/testtype.cpp b/test/testtype.cpp
index 83955e2..cdc2921 100644
--- a/test/testtype.cpp
+++ b/test/testtype.cpp
@@ -207,6 +207,12 @@ void testTypeDef()
         "        [0] float  parent=[0]  [0:1)\n"
     );
 
+    testEq(val["value"].nmembers(), 0u);
+    testEq(val["arbitrary"].nmembers(), 1u);
+    testEq(val["arbitrary.sarr"].nmembers(), 1u);
+    testEq(val["choice"].nmembers(), 2u);
+    testEq(val["achoice"].nmembers(), 2u);
+
     // try to access all field Kinds
 
     // sub-struct and scalar
@@ -586,7 +592,7 @@ void testFormat()
 
 MAIN(testtype)
 {
-    testPlan(63);
+    testPlan(68);
     testSetup();
     showSize();
     testCode();