diff --git a/prism/diagnostic.c b/prism/diagnostic.c
index fd5dce5a04..c779955eb3 100644
--- a/prism/diagnostic.c
+++ b/prism/diagnostic.c
@@ -56,6 +56,7 @@ static const char* const diagnostic_messages[PM_DIAGNOSTIC_ID_LEN] = {
     [PM_ERR_ARGUMENT_AFTER_BLOCK]               = "unexpected argument after a block argument",
     [PM_ERR_ARGUMENT_AFTER_FORWARDING_ELLIPSES] = "unexpected argument after `...`",
     [PM_ERR_ARGUMENT_BARE_HASH]                 = "unexpected bare hash argument",
+    [PM_ERR_ARGUMENT_BLOCK_FORWARDING]          = "both a block argument and a forwarding argument; only one block is allowed",
     [PM_ERR_ARGUMENT_BLOCK_MULTI]               = "multiple block arguments; only one block is allowed",
     [PM_ERR_ARGUMENT_FORMAL_CLASS]              = "invalid formal argument; formal argument cannot be a class variable",
     [PM_ERR_ARGUMENT_FORMAL_CONSTANT]           = "invalid formal argument; formal argument cannot be a constant",
diff --git a/prism/diagnostic.h b/prism/diagnostic.h
index 08a3284abf..da430b5438 100644
--- a/prism/diagnostic.h
+++ b/prism/diagnostic.h
@@ -47,6 +47,7 @@ typedef enum {
     PM_ERR_ARGUMENT_AFTER_BLOCK,
     PM_ERR_ARGUMENT_AFTER_FORWARDING_ELLIPSES,
     PM_ERR_ARGUMENT_BARE_HASH,
+    PM_ERR_ARGUMENT_BLOCK_FORWARDING,
     PM_ERR_ARGUMENT_BLOCK_MULTI,
     PM_ERR_ARGUMENT_FORMAL_CLASS,
     PM_ERR_ARGUMENT_FORMAL_CONSTANT,
diff --git a/prism/prism.c b/prism/prism.c
index 03df698449..29505a9646 100644
--- a/prism/prism.c
+++ b/prism/prism.c
@@ -813,6 +813,9 @@ typedef struct {
 
     /** The optional block attached to the call. */
     pm_node_t *block;
+
+    /** The flag indicating whether this arguments list has forwarding argument. */
+    bool has_forwarding;
 } pm_arguments_t;
 
 /**
@@ -11306,6 +11309,7 @@ parse_arguments(pm_parser_t *parser, pm_arguments_t *arguments, bool accepts_for
 
                         argument = (pm_node_t *) pm_forwarding_arguments_node_create(parser, &parser->previous);
                         parse_arguments_append(parser, arguments, argument);
+                        arguments->has_forwarding = true;
                         parsed_forwarding_arguments = true;
                         break;
                     }
@@ -12170,14 +12174,20 @@ parse_arguments_list(pm_parser_t *parser, pm_arguments_t *arguments, bool accept
         }
 
         if (block != NULL) {
-            if (arguments->block == NULL) {
+            if (arguments->block == NULL && !arguments->has_forwarding) {
                 arguments->block = (pm_node_t *) block;
             } else {
-                pm_parser_err_node(parser, (pm_node_t *) block, PM_ERR_ARGUMENT_BLOCK_MULTI);
-                if (arguments->arguments == NULL) {
-                    arguments->arguments = pm_arguments_node_create(parser);
+                if (arguments->has_forwarding) {
+                    pm_parser_err_node(parser, (pm_node_t *) block, PM_ERR_ARGUMENT_BLOCK_FORWARDING);
+                } else {
+                    pm_parser_err_node(parser, (pm_node_t *) block, PM_ERR_ARGUMENT_BLOCK_MULTI);
+                }
+                if (arguments->block != NULL) {
+                    if (arguments->arguments == NULL) {
+                        arguments->arguments = pm_arguments_node_create(parser);
+                    }
+                    pm_arguments_node_arguments_append(arguments->arguments, arguments->block);
                 }
-                pm_arguments_node_arguments_append(arguments->arguments, arguments->block);
                 arguments->block = (pm_node_t *) block;
             }
         }
diff --git a/test/prism/errors_test.rb b/test/prism/errors_test.rb
index 57c0719aa7..7648875691 100644
--- a/test/prism/errors_test.rb
+++ b/test/prism/errors_test.rb
@@ -2046,6 +2046,20 @@ module Prism
       ]
     end
 
+    def test_block_arg_and_block
+      source = 'foo(&1) { }'
+      assert_errors expression(source), source, [
+        ['multiple block arguments; only one block is allowed', 8..11]
+      ], compare_ripper: false # Ripper does not check 'both block arg and actual block given'.
+    end
+
+    def test_forwarding_arg_and_block
+      source = 'def foo(...) = foo(...) { }'
+      assert_errors expression(source), source, [
+        ['both a block argument and a forwarding argument; only one block is allowed', 24..27]
+      ], compare_ripper: false # Ripper does not check 'both block arg and actual block given'.
+    end
+
     private
 
     def assert_errors(expected, source, errors, compare_ripper: RUBY_ENGINE == "ruby")