diff --git a/expr.cpp b/expr.cpp
index 4a1a16db..8fa64f91 100644
--- a/expr.cpp
+++ b/expr.cpp
@@ -5143,9 +5143,18 @@ MemberExpr::create(Expr *e, const char *id, SourcePos p, SourcePos idpos,
                   exprType->GetString().c_str());
         return NULL;
     }
-
-    if (CastType<StructType>(exprType) != NULL)
+    if (CastType<StructType>(exprType) != NULL) {
+      const StructType *st = CastType<StructType>(exprType);
+      if (st->IsDefined()) { 
         return new StructMemberExpr(e, id, p, idpos, derefLValue);
+      }
+      else {
+        Error(p, "Member operator \"%s\" can't be applied to declared "
+              "struct \"%s\" containing an undefined struct type.", derefLValue ? "->" : ".",
+              exprType->GetString().c_str());
+        return NULL;
+      }
+    }
     else if (CastType<VectorType>(exprType) != NULL)
         return new VectorMemberExpr(e, id, p, idpos, derefLValue);
     else if (CastType<UndefinedStructType>(exprType)) {
@@ -8708,6 +8717,12 @@ NewExpr::TypeCheck() {
               "but not defined type \"%s\".", allocType->GetString().c_str());
         return NULL;
     }
+    const StructType *st = CastType<StructType>(allocType);
+    if (st != NULL && !st->IsDefined()) {
+        Error(pos, "Can't dynamically allocate storage for declared "
+              "type \"%s\" containing undefined member type.", allocType->GetString().c_str());
+        return NULL;
+    }
 
     // Otherwise we only need to make sure that if we have an expression
     // giving a number of elements to allocate that it can be converted to
diff --git a/type.cpp b/type.cpp
index 082f8910..9e8ef131 100644
--- a/type.cpp
+++ b/type.cpp
@@ -1956,6 +1956,25 @@ StructType::IsConstType() const {
 }
 
 
+bool
+StructType::IsDefined() const {
+  for (int i = 0; i < GetElementCount(); i++) {
+    const Type *t = GetElementType(i);
+    const UndefinedStructType *ust = CastType<UndefinedStructType>(t);
+    if (ust != NULL) {
+      return false;
+    }
+    const StructType *st = CastType<StructType>(t);
+    if (st != NULL) {
+      if (!st->IsDefined()) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+
 const Type *
 StructType::GetBaseType() const {
     return this;
diff --git a/type.h b/type.h
index 9093af59..94648eb1 100644
--- a/type.h
+++ b/type.h
@@ -81,15 +81,15 @@ struct Variability {
 /** Enumerant that records each of the types that inherit from the Type
     baseclass. */
 enum TypeId {
-    ATOMIC_TYPE,
-    ENUM_TYPE,
-    POINTER_TYPE,
-    ARRAY_TYPE,
-    VECTOR_TYPE,
-    STRUCT_TYPE,
-    UNDEFINED_STRUCT_TYPE,
-    REFERENCE_TYPE,
-    FUNCTION_TYPE
+  ATOMIC_TYPE,           // 0
+  ENUM_TYPE,             // 1
+  POINTER_TYPE,          // 2
+  ARRAY_TYPE,            // 3
+  VECTOR_TYPE,           // 4
+  STRUCT_TYPE,           // 5
+  UNDEFINED_STRUCT_TYPE, // 6
+  REFERENCE_TYPE,        // 7
+  FUNCTION_TYPE          // 8
 };
 
 
@@ -675,6 +675,7 @@ public:
     bool IsIntType() const;
     bool IsUnsignedType() const;
     bool IsConstType() const;
+    bool IsDefined() const;
 
     const Type *GetBaseType() const;
     const StructType *GetAsVaryingType() const;