diff --git a/spec/compiler/interpreter/autocast_spec.cr b/spec/compiler/interpreter/autocast_spec.cr
index 9efe9fda3582..0aa9e93c250c 100644
--- a/spec/compiler/interpreter/autocast_spec.cr
+++ b/spec/compiler/interpreter/autocast_spec.cr
@@ -102,5 +102,38 @@ describe Crystal::Repl::Interpreter do
           foo.color.value
         CODE
     end
+
+    it "autocasts integer var to integer (#12560)" do
+      interpret(<<-CODE).should eq(1)
+        def foo(x : Int64)
+          x
+        end
+
+        x = 1_i32
+        foo(x)
+        CODE
+    end
+
+    it "autocasts integer var to float (#12560)" do
+      interpret(<<-CODE).should eq(1)
+        def foo(x : Float64)
+          x
+        end
+
+        x = 1_i32
+        foo(x)
+        CODE
+    end
+
+    it "autocasts float32 var to float64 (#12560)" do
+      interpret(<<-CODE).should eq(1)
+        def foo(x : Float64)
+          x
+        end
+
+        x = 1.0_f32
+        foo(x)
+        CODE
+    end
   end
 end
diff --git a/src/compiler/crystal/interpreter/compiler.cr b/src/compiler/crystal/interpreter/compiler.cr
index 39296b49ad6b..1ec8d115b170 100644
--- a/src/compiler/crystal/interpreter/compiler.cr
+++ b/src/compiler/crystal/interpreter/compiler.cr
@@ -2341,9 +2341,14 @@ class Crystal::Repl::Compiler < Crystal::Visitor
 
     request_value(arg)
 
-    # We first cast the argument to the def's arg type,
-    # which is the external methods' type.
-    downcast arg, arg_type, target_def_arg_type
+    # Check number autocast but for non-literals
+    if arg_type != target_def_arg_type && arg_type.is_a?(IntegerType | FloatType) && target_def_arg_type.is_a?(IntegerType | FloatType)
+      primitive_convert(arg, arg_type, target_def_arg_type, checked: false)
+    else
+      # We first cast the argument to the def's arg type,
+      # which is the external methods' type.
+      downcast arg, arg_type, target_def_arg_type
+    end
 
     # Then we need to cast the argument to the target_def variable
     # corresponding to the argument. If for example we have this:
diff --git a/src/compiler/crystal/interpreter/primitives.cr b/src/compiler/crystal/interpreter/primitives.cr
index 3980ff1d060a..34cc22b2dbab 100644
--- a/src/compiler/crystal/interpreter/primitives.cr
+++ b/src/compiler/crystal/interpreter/primitives.cr
@@ -646,7 +646,7 @@ class Crystal::Repl::Compiler
     to_kind = integer_or_float_kind(to_type)
 
     unless from_kind && to_kind
-      node.raise "BUG: missing handling of unchecked_convert for #{from_type} (#{node.name})"
+      node.raise "BUG: missing handling of unchecked_convert for #{from_type} (#{node})"
     end
 
     primitive_convert(node, from_kind, to_kind, checked: checked)