diff --git a/expr.cpp b/expr.cpp
index b43f9e54..81680874 100644
--- a/expr.cpp
+++ b/expr.cpp
@@ -1258,6 +1258,11 @@ UnaryExpr::TypeCheck() {
                   type->GetString().c_str());
             return NULL;
         }
+        if (dynamic_cast<const UndefinedStructType *>(pt->GetBaseType())) {
+            Error(expr->pos, "Illegal to pre/post increment pointer to "
+                  "undefined struct type \"%s\".", type->GetString().c_str());
+            return NULL;
+        }
 
         return this;
     }
@@ -2296,6 +2301,16 @@ BinaryExpr::TypeCheck() {
                   "on \"%s\" type.", type1->GetString().c_str());
             return NULL;
         }
+        if (dynamic_cast<const UndefinedStructType *>(pt0->GetBaseType())) {
+            Error(pos, "Illegal to perform pointer arithmetic "
+                  "on undefined struct type \"%s\".", pt0->GetString().c_str());
+            return NULL;
+        }
+        if (dynamic_cast<const UndefinedStructType *>(pt1->GetBaseType())) {
+            Error(pos, "Illegal to perform pointer arithmetic "
+                  "on undefined struct type \"%s\".", pt1->GetString().c_str());
+            return NULL;
+        }
 
         const Type *t = Type::MoreGeneralType(type0, type1, pos, "-");
         if (t == NULL)
@@ -2331,6 +2346,11 @@ BinaryExpr::TypeCheck() {
                   "on \"%s\" type.", pt0->GetString().c_str());
             return NULL;
         }
+        if (dynamic_cast<const UndefinedStructType *>(pt0->GetBaseType())) {
+            Error(pos, "Illegal to perform pointer arithmetic "
+                  "on undefined struct type \"%s\".", pt0->GetString().c_str());
+            return NULL;
+        }
 
         const Type *offsetType = g->target.is32Bit ? 
             AtomicType::UniformInt32 : AtomicType::UniformInt64;
@@ -7336,6 +7356,14 @@ SizeOfExpr::Print() const {
 
 Expr *
 SizeOfExpr::TypeCheck() {
+    // Can't compute the size of a struct without a definition
+    if (type != NULL &&
+        dynamic_cast<const UndefinedStructType *>(type) != NULL) {
+        Error(pos, "Can't compute the size of declared but not defined "
+              "struct type \"%s\".", type->GetString().c_str());
+        return NULL;
+    }
+
     return this;
 }
 
@@ -8105,9 +8133,20 @@ NewExpr::GetType() const {
 
 Expr *
 NewExpr::TypeCheck() {
-    // Here 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 an
-    // integer of the appropriate variability.
+    // It's illegal to call new with an undefined struct type
+    if (allocType == NULL) {
+        Assert(m->errorCount > 0);
+        return NULL;
+    }
+    if (dynamic_cast<const UndefinedStructType *>(allocType) != NULL) {
+        Error(pos, "Can't dynamically allocate storage for declared "
+              "but not defined type \"%s\".", 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
+    // an integer of the appropriate variability.
     if (countExpr == NULL)
         return this;
 
diff --git a/tests_errors/undef-struct-new.ispc b/tests_errors/undef-struct-new.ispc
new file mode 100644
index 00000000..3a9037c3
--- /dev/null
+++ b/tests_errors/undef-struct-new.ispc
@@ -0,0 +1,7 @@
+// Can't dynamically allocate storage for declared but not defined type
+
+struct Foo;
+
+Foo * uniform bar() {
+    return uniform new Foo;
+}
diff --git a/tests_errors/undef-struct-ptrmath-1.ispc b/tests_errors/undef-struct-ptrmath-1.ispc
new file mode 100644
index 00000000..861c66fb
--- /dev/null
+++ b/tests_errors/undef-struct-ptrmath-1.ispc
@@ -0,0 +1,7 @@
+// Illegal to perform pointer arithmetic on undefined struct type
+
+struct Foo;
+
+Foo * uniform bar(Foo * uniform f) {
+    return f + 1;
+}
diff --git a/tests_errors/undef-struct-ptrmath-2.ispc b/tests_errors/undef-struct-ptrmath-2.ispc
new file mode 100644
index 00000000..dfaab13c
--- /dev/null
+++ b/tests_errors/undef-struct-ptrmath-2.ispc
@@ -0,0 +1,7 @@
+// Illegal to perform pointer arithmetic on undefined struct type
+
+struct Foo;
+
+Foo * uniform bar(Foo * uniform f) {
+    return 1 + f;
+}
diff --git a/tests_errors/undef-struct-ptrmath-3.ispc b/tests_errors/undef-struct-ptrmath-3.ispc
new file mode 100644
index 00000000..1fad2ac4
--- /dev/null
+++ b/tests_errors/undef-struct-ptrmath-3.ispc
@@ -0,0 +1,7 @@
+// Illegal to perform pointer arithmetic on undefined struct type
+
+struct Foo;
+
+Foo * uniform bar(Foo * uniform f) {
+    return f-1;
+}
diff --git a/tests_errors/undef-struct-ptrmath.ispc b/tests_errors/undef-struct-ptrmath.ispc
new file mode 100644
index 00000000..39b19a4e
--- /dev/null
+++ b/tests_errors/undef-struct-ptrmath.ispc
@@ -0,0 +1,7 @@
+// Illegal to pre/post increment pointer to undefined struct type
+
+struct Foo;
+
+Foo * uniform bar(Foo * uniform f) {
+    return ++f;
+}
diff --git a/tests_errors/undef-struct-sizeof.ispc b/tests_errors/undef-struct-sizeof.ispc
new file mode 100644
index 00000000..d2a2219a
--- /dev/null
+++ b/tests_errors/undef-struct-sizeof.ispc
@@ -0,0 +1,7 @@
+// Can't compute the size of declared but not defined struct type
+
+struct Foo;
+
+uniform int bar() {
+    return sizeof(Foo);
+}