diff --git a/Sources/SwiftGtkGenCore/TOMLReader.swift b/Sources/SwiftGtkGenCore/TOMLReader.swift
index 94727c7..5a5b6df 100644
--- a/Sources/SwiftGtkGenCore/TOMLReader.swift
+++ b/Sources/SwiftGtkGenCore/TOMLReader.swift
@@ -123,6 +123,9 @@ public enum TOMLReader {
             for i in s.dropFirst().indices {
                 if s[i] == "\"" { closing = i; break }
             }
+            guard closing != s.startIndex else {
+                throw TOMLReaderError.parseError(line: lineNumber, message: "Unterminated string in value")
+            }
             let value = String(s[s.index(after: s.startIndex)..<closing])
             s = String(s[s.index(after: closing)...]).trimmingCharacters(in: .whitespaces)
             return value
diff --git a/Tests/SwiftGtkGenCoreTests/TOMLReaderTests.swift b/Tests/SwiftGtkGenCoreTests/TOMLReaderTests.swift
index 1dba4b4..6fabbdf 100644
--- a/Tests/SwiftGtkGenCoreTests/TOMLReaderTests.swift
+++ b/Tests/SwiftGtkGenCoreTests/TOMLReaderTests.swift
@@ -121,3 +121,11 @@ func testInvalidInput() {
         try TOMLReader.parse(input)
     }
 }
+
+@Test("TOML reader rejects unclosed string")
+func testUnclosedString() {
+    let input = "key = \"start"
+    #expect(throws: TOMLReaderError.self) {
+        try TOMLReader.parse(input)
+    }
+}