diff --git a/src/Convert/Interface.hs b/src/Convert/Interface.hs
index d385e14..eb23173 100644
--- a/src/Convert/Interface.hs
+++ b/src/Convert/Interface.hs
@@ -570,7 +570,7 @@ inlineInstance global ranges modportBindings items partName
         makeParameterBind (x, Left t) =
             ParamType Localparam (paramTmp ++ x) t
         makeParameterBind (x, Right e) =
-            Param Localparam (TypeOf e) (paramTmp ++ x) e
+            Param Localparam UnknownType (paramTmp ++ x) e
 
         overrideParam :: Decl -> Decl
         overrideParam (Param Parameter t x e) =
diff --git a/src/Convert/Simplify.hs b/src/Convert/Simplify.hs
index 01cfd0c..0af2a8b 100644
--- a/src/Convert/Simplify.hs
+++ b/src/Convert/Simplify.hs
@@ -36,8 +36,6 @@ traverseDeclM decl = do
     case decl' of
         Param Localparam UnknownType x e ->
             insertExpr x e
-        Param Localparam (Implicit _ [(RawNum 31, RawNum 0)]) x e ->
-            insertExpr x e
         Param Localparam (Implicit sg rs) x e ->
             insertExpr x $ Cast (Left t) e
             where t = IntegerVector TLogic sg rs
diff --git a/test/basic/simplify_type.sv b/test/basic/simplify_type.sv
new file mode 100644
index 0000000..cd6d91b
--- /dev/null
+++ b/test/basic/simplify_type.sv
@@ -0,0 +1,12 @@
+module top;
+    localparam _1B1 = 1'b1;
+    localparam _1SB1 = 1'sb1;
+    localparam [31:0] _1B1_EXT = 1'b1;
+    localparam [31:0] _1SB1_EXT = 1'sb1;
+    initial begin
+        $display("%d", $clog2({_1B1, 1'b0}));
+        $display("%d", $clog2({_1SB1, 1'b0}));
+        $display("%d", $clog2({_1B1_EXT, 1'b0}));
+        $display("%d", $clog2({_1SB1_EXT, 1'b0}));
+    end
+endmodule