diff --git a/rellic/AST/ASTBuilder.cpp b/rellic/AST/ASTBuilder.cpp
index fd77fd3a..21e64fed 100644
--- a/rellic/AST/ASTBuilder.cpp
+++ b/rellic/AST/ASTBuilder.cpp
@@ -162,10 +162,16 @@ clang::Expr *ASTBuilder::CreateNull() {
   return CreateCStyleCast(ctx.VoidPtrTy, lit);
 };
 
-clang::Expr *ASTBuilder::CreateUndef(clang::QualType type) {
+clang::Expr *ASTBuilder::CreateUndefInteger(clang::QualType type) {
+  auto val{llvm::APInt::getNullValue(ctx.getTypeSize(type))};
+  auto lit{CreateIntLit(val)};
+  return lit;
+};
+
+clang::Expr *ASTBuilder::CreateUndefPointer(clang::QualType type) {
   auto null{CreateNull()};
   auto cast{CreateCStyleCast(ctx.getPointerType(type), null)};
-  return CreateDeref(cast);
+  return cast;
 };
 
 clang::IdentifierInfo *ASTBuilder::CreateIdentifier(std::string name) {
diff --git a/rellic/AST/ASTBuilder.h b/rellic/AST/ASTBuilder.h
index d140e9e4..06f99ba9 100644
--- a/rellic/AST/ASTBuilder.h
+++ b/rellic/AST/ASTBuilder.h
@@ -54,7 +54,8 @@ class ASTBuilder {
   };
   // Special values
   clang::Expr *CreateNull();
-  clang::Expr *CreateUndef(clang::QualType type);
+  clang::Expr *CreateUndefPointer(clang::QualType type);
+  clang::Expr *CreateUndefInteger(clang::QualType type);
   // Identifiers
   clang::IdentifierInfo *CreateIdentifier(std::string name);
   // Variable declaration
diff --git a/rellic/AST/IRToASTVisitor.cpp b/rellic/AST/IRToASTVisitor.cpp
index 9f4c48fd..03880df5 100644
--- a/rellic/AST/IRToASTVisitor.cpp
+++ b/rellic/AST/IRToASTVisitor.cpp
@@ -150,11 +150,18 @@ clang::Expr *IRToASTVisitor::CreateLiteralExpr(llvm::Constant *constant) {
     } break;
     // Integers
     case llvm::Type::IntegerTyID: {
-      auto val{llvm::cast<llvm::ConstantInt>(constant)->getValue()};
-      if (val.getBitWidth() == 1U) {
-        result = ast.CreateIntLit(val);
+      if (llvm::isa<llvm::ConstantInt>(constant)) {
+        auto ci = llvm::cast<llvm::ConstantInt>(constant);
+        auto val{ci->getValue()};
+        if (val.getBitWidth() == 1U) {
+          result = ast.CreateIntLit(val);
+        } else {
+          result = ast.CreateAdjustedIntLit(val);
+        }
+      } else if (llvm::isa<llvm::UndefValue>(constant)) {
+        result = ast.CreateUndefInteger(c_type);
       } else {
-        result = ast.CreateAdjustedIntLit(val);
+        LOG(FATAL) << "Unsupported integer constant";
       }
     } break;
 
@@ -162,7 +169,7 @@ clang::Expr *IRToASTVisitor::CreateLiteralExpr(llvm::Constant *constant) {
       if (llvm::isa<llvm::ConstantPointerNull>(constant)) {
         result = ast.CreateNull();
       } else if (llvm::isa<llvm::UndefValue>(constant)) {
-        result = ast.CreateUndef(c_type);
+        result = ast.CreateUndefPointer(c_type);
       } else {
         LOG(FATAL) << "Unsupported pointer constant";
       }
diff --git a/unittests/AST/ASTBuilder.cpp b/unittests/AST/ASTBuilder.cpp
index 70cdfaea..68d0f630 100644
--- a/unittests/AST/ASTBuilder.cpp
+++ b/unittests/AST/ASTBuilder.cpp
@@ -268,21 +268,29 @@ TEST_SUITE("ASTBuilder::CreateNull") {
 }
 
 TEST_SUITE("ASTBuilder::CreateUndef") {
-  SCENARIO("Create clang::Expr whose value is undefined") {
+  SCENARIO("Create clang::Expr to stand in for LLVM's 'undef' values") {
     GIVEN("Empty clang::ASTContext") {
       auto unit{GetASTUnit()};
       auto &ctx{unit->getASTContext()};
       rellic::ASTBuilder ast(*unit);
+      GIVEN("an unsigned integer type") {
+        auto type{ctx.UnsignedIntTy};
+        THEN(
+            "return a value that satisfied LLVM's undef semantics (aka "
+            "anything)") {
+          auto expr{ast.CreateUndefInteger(type)};
+          REQUIRE(expr != nullptr);
+          CHECK(expr->getType() == ctx.UnsignedIntTy);
+        }
+      }
       GIVEN("an arbitrary type t") {
         auto type{ctx.DoubleTy};
-        THEN("return a null pointer dereference of type t") {
-          auto expr{ast.CreateUndef(type)};
+        THEN("return an undef pointer (we use null pointers) of type t") {
+          auto expr{ast.CreateUndefPointer(type)};
           REQUIRE(expr != nullptr);
-          CHECK(expr->getType() == ctx.DoubleTy);
-          auto deref{clang::dyn_cast<clang::UnaryOperator>(expr)};
-          REQUIRE(deref != nullptr);
-          CHECK(deref->getOpcode() == clang::UO_Deref);
-          IsNullPtrExprCheck(ctx, deref->getSubExpr()->IgnoreCasts());
+          auto double_ptr_ty{ctx.getPointerType(ctx.DoubleTy)};
+          CHECK(expr->getType() == double_ptr_ty);
+          IsNullPtrExprCheck(ctx, expr->IgnoreCasts());
         }
       }
     }