diff --git a/nac3type/src/inference.rs b/nac3type/src/inference.rs
index c7f89ce58e..f37c383570 100644
--- a/nac3type/src/inference.rs
+++ b/nac3type/src/inference.rs
@@ -16,15 +16,24 @@ fn find_subst(
         }
     }
 
+    let mut substituted = false;
     if let TypeVariable(id) = b.as_ref() {
         if let Some(c) = sub.get(&id) {
             b = c.clone();
+            substituted = true;
         }
     }
 
     match (a.as_ref(), b.as_ref()) {
         (BotType, _) => Ok(()),
         (TypeVariable(id_a), TypeVariable(id_b)) => {
+            if substituted {
+                return if id_a == id_b {
+                    Ok(())
+                } else {
+                    Err("different variables".to_string())
+                };
+            }
             let v_a = ctx.get_variable(*id_a);
             let v_b = ctx.get_variable(*id_b);
             if v_b.bound.len() > 0 {
@@ -224,6 +233,17 @@ mod tests {
             Err("different domain".to_string())
         );
 
+        assert_eq!(
+            resolve_call(
+                &ctx,
+                None,
+                "float",
+                create_tuple(vec![]),
+                &mut assumptions
+            ),
+            Err("different parametric types".to_string())
+        );
+
         let v1 = ctx.add_variable(VarDef {
             name: "V1",
             bound: vec![
@@ -269,6 +289,10 @@ mod tests {
         let mut ctx = basic_ctx();
         let mut assumptions = HashMap::new();
 
+        let v0 = Rc::new(TypeVariable(ctx.add_variable(VarDef {
+            name: "V0",
+            bound: vec![],
+        })));
         let v1 = Rc::new(TypeVariable(ctx.add_variable(VarDef {
             name: "V1",
             bound: vec![
@@ -340,6 +364,26 @@ mod tests {
             ),
             Ok(Some(v1.clone()))
         );
+        assert_eq!(
+            resolve_call(
+                &ctx,
+                Some(v0.clone()),
+                "__add__",
+                create_tuple(vec![v2.clone()]),
+                &mut assumptions
+            ),
+            Err("unbounded type var".to_string())
+        );
+        assert_eq!(
+            resolve_call(
+                &ctx,
+                Some(v1.clone()),
+                "__add__",
+                create_tuple(vec![v0.clone()]),
+                &mut assumptions
+            ),
+            Err("different domain".to_string())
+        );
         assert_eq!(
             resolve_call(
                 &ctx,
@@ -350,6 +394,16 @@ mod tests {
             ),
             Err("different domain".to_string())
         );
+        assert_eq!(
+            resolve_call(
+                &ctx,
+                Some(v1.clone()),
+                "__add__",
+                create_tuple(vec![v3.clone()]),
+                &mut assumptions
+            ),
+            Err("different domain".to_string())
+        );
         assert_eq!(
             resolve_call(
                 &ctx,
@@ -370,7 +424,66 @@ mod tests {
             ),
             Err("no such function".to_string())
         );
+    }
 
+    #[test]
+    fn test_multi_generic() {
+        let mut ctx = basic_ctx();
+        let mut assumptions = HashMap::new();
+        let v0 = Rc::new(TypeVariable(ctx.add_variable(VarDef {
+            name: "V0",
+            bound: vec![],
+        })));
+        let v1 = Rc::new(TypeVariable(ctx.add_variable(VarDef {
+            name: "V1",
+            bound: vec![],
+        })));
+        let v2 = Rc::new(TypeVariable(ctx.add_variable(VarDef {
+            name: "V2",
+            bound: vec![],
+        })));
+        let v3 = Rc::new(TypeVariable(ctx.add_variable(VarDef {
+            name: "V3",
+            bound: vec![],
+        })));
+
+        ctx.add_fn(
+            "foo",
+            FnDef {
+                args: create_tuple(vec![v0.clone(), v0.clone(), v1.clone()]),
+                result: Some(v0.clone()),
+            },
+        );
+
+        assert_eq!(
+            resolve_call(
+                &ctx,
+                None,
+                "foo",
+                create_tuple(vec![v2.clone(), v2.clone(), v2.clone()]),
+                &mut assumptions
+            ),
+            Ok(Some(v2.clone()))
+        );
+        assert_eq!(
+            resolve_call(
+                &ctx,
+                None,
+                "foo",
+                create_tuple(vec![v2.clone(), v2.clone(), v3.clone()]),
+                &mut assumptions
+            ),
+            Ok(Some(v2.clone()))
+        );
+        assert_eq!(
+            resolve_call(
+                &ctx,
+                None,
+                "foo",
+                create_tuple(vec![v2.clone(), v3.clone(), v3.clone()]),
+                &mut assumptions
+            ),
+            Err("different variables".to_string())
+        );
     }
 }
-