diff --git a/src/verilogAST.cpp b/src/verilogAST.cpp
index 3cc3b4c..ab2cfde 100644
--- a/src/verilogAST.cpp
+++ b/src/verilogAST.cpp
@@ -59,6 +59,10 @@ std::string NumericLiteral::toString() {
   if (size_str == "32" && !always_codegen_size) {
     size_str = "";
   }
+  if (size_str != "" && radix_str == "") {
+    // verilator needs decimal explicitly
+    radix_str = "d";
+  }
 
   std::string separator = "";
   if (size_str + signed_str + radix_str != "") {
diff --git a/tests/basic.cpp b/tests/basic.cpp
index 49c2aee..d3ecd29 100644
--- a/tests/basic.cpp
+++ b/tests/basic.cpp
@@ -8,7 +8,7 @@ namespace {
 
 TEST(BasicTests, TestNumericLiteral) {
   vAST::NumericLiteral n0("23", 16, false, vAST::DECIMAL);
-  EXPECT_EQ(n0.toString(), "16'23");
+  EXPECT_EQ(n0.toString(), "16'd23");
 
   vAST::NumericLiteral n1("DEADBEEF", 32, false, vAST::HEX);
   EXPECT_EQ(n1.toString(), "'hDEADBEEF");
@@ -20,16 +20,16 @@ TEST(BasicTests, TestNumericLiteral) {
   EXPECT_EQ(n3.toString(), "24'o764");
 
   vAST::NumericLiteral n4("764", 8, false);
-  EXPECT_EQ(n4.toString(), "8'764");
+  EXPECT_EQ(n4.toString(), "8'd764");
 
   vAST::NumericLiteral n5("764", 8);
-  EXPECT_EQ(n5.toString(), "8'764");
+  EXPECT_EQ(n5.toString(), "8'd764");
 
   vAST::NumericLiteral n6("764");
   EXPECT_EQ(n6.toString(), "764");
 
   vAST::NumericLiteral n7("764", 8, true);
-  EXPECT_EQ(n7.toString(), "8's764");
+  EXPECT_EQ(n7.toString(), "8'sd764");
 
   vAST::NumericLiteral n8("z", vAST::Radix::HEX);
   EXPECT_EQ(n8.toString(), "'hz");