diff --git a/Libraries/LibWeb/HTML/HTMLTableColElement.cpp b/Libraries/LibWeb/HTML/HTMLTableColElement.cpp
index 753a76b5013..48351f6b6ee 100644
--- a/Libraries/LibWeb/HTML/HTMLTableColElement.cpp
+++ b/Libraries/LibWeb/HTML/HTMLTableColElement.cpp
@@ -29,18 +29,25 @@ void HTMLTableColElement::initialize(JS::Realm& realm)
 }
 
 // https://html.spec.whatwg.org/multipage/tables.html#dom-colgroup-span
-unsigned int HTMLTableColElement::span() const
+WebIDL::UnsignedLong HTMLTableColElement::span() const
 {
     // The span IDL attribute must reflect the content attribute of the same name. It is clamped to the range [1, 1000], and its default value is 1.
     if (auto span_string = get_attribute(HTML::AttributeNames::span); span_string.has_value()) {
-        if (auto span = parse_non_negative_integer(*span_string); span.has_value())
+        if (auto span_digits = parse_non_negative_integer_digits(*span_string); span_digits.has_value()) {
+            auto span = AK::StringUtils::convert_to_int<i64>(*span_digits);
+            // NOTE: If span has no value at this point, the value must be larger than NumericLimits<i64>::max(), so return the maximum value of 1000.
+            if (!span.has_value())
+                return 1000;
             return clamp(*span, 1, 1000);
+        }
     }
     return 1;
 }
 
 WebIDL::ExceptionOr<void> HTMLTableColElement::set_span(unsigned int value)
 {
+    if (value > 2147483647)
+        value = 1;
     return set_attribute(HTML::AttributeNames::span, String::number(value));
 }
 
diff --git a/Libraries/LibWeb/HTML/HTMLTableColElement.h b/Libraries/LibWeb/HTML/HTMLTableColElement.h
index 9da04faeb45..a5d499199f9 100644
--- a/Libraries/LibWeb/HTML/HTMLTableColElement.h
+++ b/Libraries/LibWeb/HTML/HTMLTableColElement.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <LibWeb/HTML/HTMLElement.h>
+#include <LibWeb/WebIDL/Types.h>
 
 namespace Web::HTML {
 
@@ -17,8 +18,8 @@ class HTMLTableColElement final : public HTMLElement {
 public:
     virtual ~HTMLTableColElement() override;
 
-    unsigned span() const;
-    WebIDL::ExceptionOr<void> set_span(unsigned);
+    WebIDL::UnsignedLong span() const;
+    WebIDL::ExceptionOr<void> set_span(WebIDL::UnsignedLong);
 
 private:
     HTMLTableColElement(DOM::Document&, DOM::QualifiedName);
diff --git a/Tests/LibWeb/Text/expected/HTML/unsigned-long-reflection.txt b/Tests/LibWeb/Text/expected/HTML/unsigned-long-reflection.txt
index cb4ba245cff..661c8c059bc 100644
--- a/Tests/LibWeb/Text/expected/HTML/unsigned-long-reflection.txt
+++ b/Tests/LibWeb/Text/expected/HTML/unsigned-long-reflection.txt
@@ -46,6 +46,30 @@ canvas.getAttribute("height") after canvas.setAttribute("height", "4294967296"):
 canvas.height after canvas.setAttribute("height", "4294967296"): 150
 canvas.getAttribute("height") after canvas.height = 4294967296: 0
 canvas.height after canvas.height = 4294967296: 0
+colgroup.getAttribute("span") after colgroup.setAttribute("span", "0"): 0
+colgroup.span after colgroup.setAttribute("span", "0"): 1
+colgroup.getAttribute("span") after colgroup.span = 0: 0
+colgroup.span after colgroup.span = 0: 1
+colgroup.getAttribute("span") after colgroup.setAttribute("span", "1"): 1
+colgroup.span after colgroup.setAttribute("span", "1"): 1
+colgroup.getAttribute("span") after colgroup.span = 1: 1
+colgroup.span after colgroup.span = 1: 1
+colgroup.getAttribute("span") after colgroup.setAttribute("span", "2147483647"): 2147483647
+colgroup.span after colgroup.setAttribute("span", "2147483647"): 1000
+colgroup.getAttribute("span") after colgroup.span = 2147483647: 2147483647
+colgroup.span after colgroup.span = 2147483647: 1000
+colgroup.getAttribute("span") after colgroup.setAttribute("span", "2147483648"): 2147483648
+colgroup.span after colgroup.setAttribute("span", "2147483648"): 1000
+colgroup.getAttribute("span") after colgroup.span = 2147483648: 1
+colgroup.span after colgroup.span = 2147483648: 1
+colgroup.getAttribute("span") after colgroup.setAttribute("span", "4294967295"): 4294967295
+colgroup.span after colgroup.setAttribute("span", "4294967295"): 1000
+colgroup.getAttribute("span") after colgroup.span = 4294967295: 1
+colgroup.span after colgroup.span = 4294967295: 1
+colgroup.getAttribute("span") after colgroup.setAttribute("span", "4294967296"): 4294967296
+colgroup.span after colgroup.setAttribute("span", "4294967296"): 1000
+colgroup.getAttribute("span") after colgroup.span = 4294967296: 0
+colgroup.span after colgroup.span = 4294967296: 1
 img.getAttribute("height") after img.setAttribute("height", "0"): 0
 img.height after img.setAttribute("height", "0"): 0
 img.getAttribute("height") after img.height = 0: 0
diff --git a/Tests/LibWeb/Text/input/HTML/unsigned-long-reflection.html b/Tests/LibWeb/Text/input/HTML/unsigned-long-reflection.html
index 8a596d9d0a8..d1ffbaec207 100644
--- a/Tests/LibWeb/Text/input/HTML/unsigned-long-reflection.html
+++ b/Tests/LibWeb/Text/input/HTML/unsigned-long-reflection.html
@@ -45,6 +45,7 @@
 
         testProperty("canvas", "width", (canvas) => canvas.width, (canvas, value) => canvas.width = value);
         testProperty("canvas", "height", (canvas) => canvas.height, (canvas, value) => canvas.height = value);
+        testProperty("colgroup", "span", (colgroup) => colgroup.span, (colgroup, value) => colgroup.span = value);
         testProperty("img", "height", (img) => img.height, (img, value) => img.height = value);
         testProperty("img", "hspace", (img) => img.hspace, (img, value) => img.hspace = value);
         testProperty("img", "width", (img) => img.width, (img, value) => img.width = value);