diff --git a/.release-notes/4278.md b/.release-notes/4278.md
new file mode 100644
index 0000000000..32067dc2d8
--- /dev/null
+++ b/.release-notes/4278.md
@@ -0,0 +1,3 @@
+## Fix crash when handling parameters with invalid types
+
+Fixes a compiler assert when checking a parameter for autorecovery that has an invalid type.
diff --git a/src/libponyc/expr/call.c b/src/libponyc/expr/call.c
index 0e64135f18..6921b4490c 100644
--- a/src/libponyc/expr/call.c
+++ b/src/libponyc/expr/call.c
@@ -281,7 +281,7 @@ static bool check_arg_types(pass_opt_t* opt, ast_t* params, ast_t* positional,
 
     errorframe_t info = NULL;
     ast_t* wp_type = consume_type(p_type, TK_NONE, false);
-    if(check_auto_recover_newref(wp_type, arg))
+    if((wp_type != NULL) && check_auto_recover_newref(wp_type, arg))
     {
       token_id arg_cap = ast_id(cap_fetch(wp_type));
       ast_t* recovered_arg_type = recover_type(arg_type, arg_cap);