diff --git a/packages/coln-flir-rs/src/ir/mod.rs b/packages/coln-flir-rs/src/ir/mod.rs
index 7d3570b1..5a146e15 100644
--- a/packages/coln-flir-rs/src/ir/mod.rs
+++ b/packages/coln-flir-rs/src/ir/mod.rs
@@ -36,8 +36,8 @@ impl Serialize for BuiltinTy {
         S: Serializer,
     {
         match self {
-            BuiltinTy::BuiltinInt => serializer.serialize_str("int"),
-            BuiltinTy::BuiltinStr => serializer.serialize_str("string"),
+            BuiltinTy::BuiltinInt => serializer.serialize_str("builtinInt"),
+            BuiltinTy::BuiltinStr => serializer.serialize_str("builtinString"),
         }
     }
 }
@@ -49,9 +49,12 @@ impl<'de> Deserialize<'de> for BuiltinTy {
     {
         let s = String::deserialize(deserializer)?;
         match s.as_str() {
-            "int" => Ok(BuiltinTy::BuiltinInt),
-            "string" => Ok(BuiltinTy::BuiltinStr),
-            _ => Err(DeError::unknown_variant(&s, &["int", "string"])),
+            "builtinInt" => Ok(BuiltinTy::BuiltinInt),
+            "builtinString" => Ok(BuiltinTy::BuiltinStr),
+            _ => Err(DeError::unknown_variant(
+                &s,
+                &["builtinInt", "builtinString"],
+            )),
         }
     }
 }
@@ -59,8 +62,14 @@ impl<'de> Deserialize<'de> for BuiltinTy {
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(tag = "tag", rename_all = "camelCase")]
 pub enum ColType {
-    RowId { path: Path },
-    BuiltinTy { builtin_ty: BuiltinTy },
+    RowId {
+        path: Path,
+    },
+    #[serde(rename = "builtin")]
+    BuiltinTy {
+        #[serde(rename = "type")]
+        builtin_ty: BuiltinTy,
+    },
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
diff --git a/packages/coln-flir-rs/tests/data/Prim.json b/packages/coln-flir-rs/tests/data/Prim.json
new file mode 100644
index 00000000..dd64b14a
--- /dev/null
+++ b/packages/coln-flir-rs/tests/data/Prim.json
@@ -0,0 +1 @@
+{"entities":[{"path":[["T"],["N"]],"value":{"entityVariant":{"tag":"table"},"columns":[{"path":[["a"]],"type":{"tag":"builtin","type":"builtinInt"}}],"primaryKey":null}},{"path":[["T"],["S"]],"value":{"entityVariant":{"tag":"table"},"columns":[{"path":[["a"]],"type":{"tag":"builtin","type":"builtinString"}}],"primaryKey":null}}],"rules":[{"path":[["T"],["N"],["foreignKey"]],"value":{"ruleVariant":"enforced","varNames":[[["a"]]],"varTypes":[{"tag":"builtin","type":"builtinInt"}],"antecedents":[{"tag":"atom","atom":{"entity":[["T"],["N"]],"rowId":null,"values":[{"column":0,"term":{"tag":"var","index":0}}]}}],"consequents":[]}},{"path":[["T"],["S"],["foreignKey"]],"value":{"ruleVariant":"enforced","varNames":[[["a"]]],"varTypes":[{"tag":"builtin","type":"builtinString"}],"antecedents":[{"tag":"atom","atom":{"entity":[["T"],["S"]],"rowId":null,"values":[{"column":0,"term":{"tag":"var","index":0}}]}}],"consequents":[]}}]}
\ No newline at end of file
diff --git a/packages/coln-flir-rs/tests/test_theory.rs b/packages/coln-flir-rs/tests/test_theory.rs
index 0e9ee129..21f75d2a 100644
--- a/packages/coln-flir-rs/tests/test_theory.rs
+++ b/packages/coln-flir-rs/tests/test_theory.rs
@@ -7,7 +7,7 @@ mod common;
 use coln_flir_rs::ir::Path;
 
 // TODO add more theory json files
-const THEORY_FIXTURES: &[&str] = &["Graph.json"];
+const THEORY_FIXTURES: &[&str] = &["Graph.json", "Prim.json"];
 
 #[test]
 fn deserialises_all_theory_fixtures() {