diff --git a/source/core/slang-string-util.cpp b/source/core/slang-string-util.cpp
index 6f1dc2ccb8..3da4084618 100644
--- a/source/core/slang-string-util.cpp
+++ b/source/core/slang-string-util.cpp
@@ -690,16 +690,18 @@ String StringUtil::replaceAll(
     }
 
     int radix = 10;
+    auto isDigit = CharUtil::isDigit;
     auto getDigit = CharUtil::getDecimalDigitValue;
     if (cur + 1 < end && *cur == '0' && (*(cur + 1) == 'x' || *(cur + 1) == 'X'))
     {
         radix = 16;
+        isDigit = CharUtil::isHexDigit;
         getDigit = CharUtil::getHexDigitValue;
         cur += 2;
     }
 
     // We need at least one digit
-    if (cur >= end || !CharUtil::isDigit(*cur))
+    if (cur >= end || !isDigit(*cur))
     {
         return SLANG_FAIL;
     }
diff --git a/tools/slang-cpp-parser/node.cpp b/tools/slang-cpp-parser/node.cpp
index 16484ead39..af15508580 100644
--- a/tools/slang-cpp-parser/node.cpp
+++ b/tools/slang-cpp-parser/node.cpp
@@ -688,6 +688,26 @@ void ClassLikeNode::dump(int indentCount, StringBuilder& out)
 
     out << " {\n";
 
+    if (m_guid != Guid())
+    {
+        _indent(indentCount + 1, out);
+        StringUtil::appendFormat(
+            out,
+            "COM_INTERFACE(0x%08lx, 0x%04hx, 0x%04hx, {0x%02hhx, 0x%02hhx, 0x%02hhx, 0x%02hhx, "
+            "0x%02hhx, 0x%02hhx, 0x%02hhx, 0x%02hhx})\n",
+            m_guid.data1,
+            m_guid.data2,
+            m_guid.data3,
+            m_guid.data4[0],
+            m_guid.data4[1],
+            m_guid.data4[2],
+            m_guid.data4[3],
+            m_guid.data4[4],
+            m_guid.data4[5],
+            m_guid.data4[6],
+            m_guid.data4[7]);
+    }
+
     for (Node* child : m_children)
     {
         child->dump(indentCount + 1, out);
diff --git a/tools/slang-cpp-parser/node.h b/tools/slang-cpp-parser/node.h
index 4dad9473e0..04cee8d715 100644
--- a/tools/slang-cpp-parser/node.h
+++ b/tools/slang-cpp-parser/node.h
@@ -316,7 +316,7 @@ struct ClassLikeNode : public ScopeNode
     virtual void dump(int indent, StringBuilder& out) SLANG_OVERRIDE;
 
     ClassLikeNode(Kind kind)
-        : Super(kind), m_origin(nullptr), m_typeSet(nullptr), m_superNode(nullptr)
+        : Super(kind), m_origin(nullptr), m_typeSet(nullptr), m_superNode(nullptr), m_guid(Guid())
     {
         SLANG_ASSERT(kind == Kind::ClassType || kind == Kind::StructType);
     }
@@ -333,6 +333,8 @@ struct ClassLikeNode : public ScopeNode
     Token m_super;              ///< Super class name
     ClassLikeNode* m_superNode; ///< If this is a class/struct, the type it is derived from (or
                                 ///< nullptr if base)
+
+    Guid m_guid; ///< The guid associated with this type
 };
 
 struct CallableNode : public Node
diff --git a/tools/slang-cpp-parser/parser.cpp b/tools/slang-cpp-parser/parser.cpp
index 9fcf6a6b98..32f68216b3 100644
--- a/tools/slang-cpp-parser/parser.cpp
+++ b/tools/slang-cpp-parser/parser.cpp
@@ -1109,32 +1109,58 @@ SlangResult Parser::_parseSpecialMacro()
     Token name;
     SLANG_RETURN_ON_FAIL(expect(TokenType::Identifier, &name));
 
-    List<Token> params;
+    const UnownedStringSlice suffix = name.getContent().tail(m_options->m_markPrefix.getLength());
 
-    if (m_reader.peekTokenType() == TokenType::LParent)
+    if (suffix == "COM_INTERFACE")
     {
-        // Mark the start
-        auto startCursor = m_reader.getCursor();
+        return _parseGuid();
+    }
 
-        // Consume the params
+    if (m_reader.peekTokenType() == TokenType::LParent)
+    {
         SLANG_RETURN_ON_FAIL(_consumeBalancedParens());
+    }
 
-        auto endCursor = m_reader.getCursor();
-        m_reader.setCursor(startCursor);
+    return SLANG_OK;
+}
 
-        while (!m_reader.isAtCursor(endCursor))
+SlangResult Parser::_parseGuid()
+{
+    Guid guid{};
+    Token guidToken;
+    Int value;
+
+    SLANG_RETURN_ON_FAIL(expect(TokenType::LParent));
+
+    SLANG_RETURN_ON_FAIL(expect(TokenType::IntegerLiteral, &guidToken));
+    StringUtil::parseInt(guidToken.getContent(), value);
+    guid.data1 = value;
+    SLANG_RETURN_ON_FAIL(expect(TokenType::Comma));
+    SLANG_RETURN_ON_FAIL(expect(TokenType::IntegerLiteral, &guidToken));
+    StringUtil::parseInt(guidToken.getContent(), value);
+    guid.data2 = value;
+    SLANG_RETURN_ON_FAIL(expect(TokenType::Comma));
+    SLANG_RETURN_ON_FAIL(expect(TokenType::IntegerLiteral, &guidToken));
+    StringUtil::parseInt(guidToken.getContent(), value);
+    guid.data3 = value;
+    SLANG_RETURN_ON_FAIL(expect(TokenType::Comma));
+    SLANG_RETURN_ON_FAIL(expect(TokenType::LBrace));
+    for (Index i = 0; i < 8; ++i)
+    {
+        SLANG_RETURN_ON_FAIL(expect(TokenType::IntegerLiteral, &guidToken));
+        StringUtil::parseInt(guidToken.getContent(), value);
+        guid.data4[i] = value;
+        if (i < 7)
         {
-            params.add(m_reader.advanceToken());
+            SLANG_RETURN_ON_FAIL(expect(TokenType::Comma));
         }
     }
+    SLANG_RETURN_ON_FAIL(expect(TokenType::RBrace));
+    SLANG_RETURN_ON_FAIL(expect(TokenType::RParent));
 
-    // Can do special handling here
-    const UnownedStringSlice suffix = name.getContent().tail(m_options->m_markPrefix.getLength());
+    ClassLikeNode* node = as<ClassLikeNode>(m_currentScope);
 
-    if (suffix == "COM_INTERFACE")
-    {
-        // TODO(JS): It's a com interface. Extact the GUID
-    }
+    node->m_guid = guid;
 
     return SLANG_OK;
 }
diff --git a/tools/slang-cpp-parser/parser.h b/tools/slang-cpp-parser/parser.h
index c3ccf9656a..675fdccde1 100644
--- a/tools/slang-cpp-parser/parser.h
+++ b/tools/slang-cpp-parser/parser.h
@@ -44,6 +44,7 @@ class Parser
 
     SlangResult _parseTypeDef();
     SlangResult _parseEnum();
+    SlangResult _parseGuid();
     SlangResult _parseMarker();
     SlangResult _parseSpecialMacro();
 
diff --git a/tools/slang-cpp-parser/unit-test.cpp b/tools/slang-cpp-parser/unit-test.cpp
index 7320e708e8..da8542be45 100644
--- a/tools/slang-cpp-parser/unit-test.cpp
+++ b/tools/slang-cpp-parser/unit-test.cpp
@@ -42,6 +42,8 @@ struct TestState
 
 static const char someSource[] = "class ISomeInterface\n"
                                  "{\n"
+                                 "    SLANG_COM_INTERFACE(0x514027d8, 0x23d1, 0x4093, "
+                                 "{0x94,0x85,0xb9,0x2c,0x06,0x95,0x7f,0x5e})\n"
                                  "    public:\n"
                                  "    virtual int SLANG_MCALL someMethod(int a, int b) const = 0;\n"
                                  "    virtual float SLANG_MCALL anotherMethod(float a) = 0;\n"