diff --git a/src/ExpressionParser.php b/src/ExpressionParser.php
index ddfbd2a47..9e3debeea 100644
--- a/src/ExpressionParser.php
+++ b/src/ExpressionParser.php
@@ -735,7 +735,7 @@ class ExpressionParser
             }
 
             $name = null;
-            if ($namedArguments && (($token = $stream->nextIf(Token::OPERATOR_TYPE, '=')) || ($token = $stream->nextIf(Token::PUNCTUATION_TYPE, ':')))) {
+            if ($namedArguments && (($token = $stream->nextIf(Token::OPERATOR_TYPE, '=')) || (!$definition && $token = $stream->nextIf(Token::PUNCTUATION_TYPE, ':')))) {
                 if (!$value instanceof NameExpression) {
                     throw new SyntaxError(\sprintf('A parameter name must be a string, "%s" given.', \get_class($value)), $token->getLine(), $stream->getSourceContext());
                 }
diff --git a/tests/Fixtures/tags/macro/colon_not_supported_as_default_separator.test b/tests/Fixtures/tags/macro/colon_not_supported_as_default_separator.test
new file mode 100644
index 000000000..6b0bb25fb
--- /dev/null
+++ b/tests/Fixtures/tags/macro/colon_not_supported_as_default_separator.test
@@ -0,0 +1,10 @@
+--TEST--
+"macro" tag does not support : as a separator in definition, only = is supported
+--TEMPLATE--
+{% macro test(foo: "foo") -%}
+    {{ foo }}
+{%- endmacro %}
+--DATA--
+return []
+--EXCEPTION--
+Twig\Error\SyntaxError: Arguments must be separated by a comma. Unexpected token "punctuation" of value ":" ("punctuation" expected with value ",") in "index.twig" at line 2.