diff --git a/templates/cc/msg.go b/templates/cc/msg.go
index 81f336d17..46cd290fe 100644
--- a/templates/cc/msg.go
+++ b/templates/cc/msg.go
@@ -116,6 +116,11 @@ bool Validate(const {{ class . }}& m, pgv::ValidationMsg* err) {
 		{{ range .NonOneOfFields }}
 			{{- render (context .) -}}
 		{{ end -}}
+		{{ range .SyntheticOneOfFields }}
+			if ({{ hasAccessor (context .) }}) {
+				{{ render (context .) }}
+			}
+		{{ end }}
 		{{ range .RealOneOfs }}
 			switch (m.{{ .Name }}_case()) {
 				{{ range .Fields -}}
diff --git a/templates/java/msg.go b/templates/java/msg.go
index 0c58760da..2cf8fd3c0 100644
--- a/templates/java/msg.go
+++ b/templates/java/msg.go
@@ -15,6 +15,9 @@ const msgInnerTpl = `
 	{{- range .NonOneOfFields }}
 		{{ renderConstants (context .) }}
 	{{ end }}
+	{{ range .SyntheticOneOfFields }}
+		{{ renderConstants (context .) }}
+	{{ end }}
 	{{ range .RealOneOfs }}
 		{{ template "oneOfConst" . }}
 	{{ end }}
@@ -27,6 +30,11 @@ const msgInnerTpl = `
 	{{ range .NonOneOfFields -}}
 		{{ render (context .) }}
 	{{ end -}}
+	{{ range .SyntheticOneOfFields }}
+		if ({{ hasAccessor (context .) }}) {
+			{{ render (context .) }}
+		}
+	{{ end }}
 	{{ range .RealOneOfs }}
 		{{ template "oneOf" . }}
 	{{- end -}}