diff --git a/autotests/foldingtest.cpp b/autotests/foldingtest.cpp
--- a/autotests/foldingtest.cpp
+++ b/autotests/foldingtest.cpp
@@ -178,16 +178,10 @@
         highlighter.setDefinition(def);
         highlighter.highlightFile(inFile, outFile);
 
-        const auto diffExecutable = QStandardPaths::findExecutable(QStringLiteral("diff"));
-        if (!diffExecutable.isEmpty()) {
-            QProcess proc;
-            proc.setProcessChannelMode(QProcess::ForwardedChannels);
-            proc.start(diffExecutable, {QStringLiteral("-u"), refFile, outFile});
-            QVERIFY(proc.waitForFinished());
-            QCOMPARE(proc.exitCode(), 0);
-        } else {
-            qDebug() << "Skipping part of the test since the 'diff' executable is not in PATH";
-        }
+        /**
+         * compare results
+         */
+        compareFiles(refFile, outFile);
     }
 
 };
diff --git a/autotests/htmlhighlighter_test.cpp b/autotests/htmlhighlighter_test.cpp
--- a/autotests/htmlhighlighter_test.cpp
+++ b/autotests/htmlhighlighter_test.cpp
@@ -107,16 +107,10 @@
         highlighter.setOutputFile(outFile);
         highlighter.highlightFile(inFile);
 
-        const auto diffExecutable = QStandardPaths::findExecutable(QStringLiteral("diff"));
-        if (!diffExecutable.isEmpty()) {
-            QProcess proc;
-            proc.setProcessChannelMode(QProcess::ForwardedChannels);
-            proc.start(diffExecutable, {QStringLiteral("-u"), refFile, outFile});
-            QVERIFY(proc.waitForFinished());
-            QCOMPARE(proc.exitCode(), 0);
-        } else {
-            qDebug() << "Skipping part of the test since the 'diff' executable is not in PATH";
-        }
+        /**
+         * compare results
+         */
+        compareFiles(refFile, outFile);
     }
 
 };
diff --git a/autotests/test-config.h.in b/autotests/test-config.h.in
--- a/autotests/test-config.h.in
+++ b/autotests/test-config.h.in
@@ -21,7 +21,11 @@
     SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
+#include <QFile>
+#include <QProcess>
+#include <QStandardPaths>
 #include <QString>
+#include <qtest.h>
 
 #include <repository.h>
 
@@ -34,12 +38,51 @@
  *
  * @param repository repository to init search paths
  */
-static void initRepositorySearchPaths(KSyntaxHighlighting::Repository &repository)
+void initRepositorySearchPaths(KSyntaxHighlighting::Repository &repository)
 {
 #ifdef HAS_SYNTAX_RESOURCE
     Q_UNUSED(repository)
 #else
     repository.addCustomSearchPath(QStringLiteral("@CMAKE_SOURCE_DIR@/data"));
     repository.addCustomSearchPath(QStringLiteral("@CMAKE_BINARY_DIR@/data"));
 #endif
 }
+
+/**
+ * helper to compare files
+ * @param refFile reference file
+ * @param outFile output file
+ */
+void compareFiles(const QString &refFile, const QString &outFile)
+{
+    /**
+     * quick compare, all fine, if no diffs!
+     */
+    QFile ref(refFile);
+    QFile out(outFile);
+    QVERIFY(ref.open(QIODevice::ReadOnly));
+    QVERIFY(out.open(QIODevice::ReadOnly));
+    const bool equalResults = ref.readAll() == out.readAll();
+    if (equalResults) {
+        return;
+    }
+
+    /**
+     * elaborate diff output, if possible
+     */
+    const auto diffExecutable = QStandardPaths::findExecutable(QStringLiteral("diff"));
+    if (!diffExecutable.isEmpty()) {
+        QProcess proc;
+        proc.setProcessChannelMode(QProcess::ForwardedChannels);
+        proc.start(diffExecutable, {QStringLiteral("-u"), refFile, outFile});
+        QVERIFY(proc.waitForFinished());
+        QCOMPARE(proc.exitCode(), 0);
+    } else {
+        qDebug() << "Skipping differences output as the 'diff' executable is not in the PATH";
+    }
+
+    /**
+     * if we arrive here, all lost!
+     */
+    QVERIFY(equalResults);
+}
diff --git a/autotests/testhighlighter.cpp b/autotests/testhighlighter.cpp
--- a/autotests/testhighlighter.cpp
+++ b/autotests/testhighlighter.cpp
@@ -33,8 +33,6 @@
 #include <QDirIterator>
 #include <QFile>
 #include <QObject>
-#include <QProcess>
-#include <QStandardPaths>
 #include <QTextStream>
 #include <qtest.h>
 
@@ -176,16 +174,10 @@
         highlighter.setDefinition(def);
         highlighter.highlightFile(inFile, outFile);
 
-        const auto diffExecutable = QStandardPaths::findExecutable(QStringLiteral("diff"));
-        if (!diffExecutable.isEmpty()) {
-            QProcess proc;
-            proc.setProcessChannelMode(QProcess::ForwardedChannels);
-            proc.start(diffExecutable, {QStringLiteral("-u"), refFile, outFile});
-            QVERIFY(proc.waitForFinished());
-            QCOMPARE(proc.exitCode(), 0);
-        } else {
-            qDebug() << "Skipping part of the test since the 'diff' executable is not in PATH";
-        }
+        /**
+         * compare results
+         */
+        compareFiles(refFile, outFile);
     }
 
 };
diff --git a/src/lib/abstracthighlighter.cpp b/src/lib/abstracthighlighter.cpp
--- a/src/lib/abstracthighlighter.cpp
+++ b/src/lib/abstracthighlighter.cpp
@@ -127,12 +127,13 @@
     auto defData = DefinitionData::get(d->m_definition);
     auto newState = state;
     auto stateData = StateData::get(newState);
-    if (stateData->initialContext() && DefinitionData::get(stateData->initialContext()->definition()) != defData) {
+    if (stateData->m_defData && defData != stateData->m_defData) {
         qCDebug(Log) << "Got invalid state, resetting.";
         stateData->clear();
     }
     if (stateData->isEmpty()) {
         stateData->push(defData->initialContext(), QStringList());
+        stateData->m_defData = defData;
     }
 
     // process empty lines
diff --git a/src/lib/state.cpp b/src/lib/state.cpp
--- a/src/lib/state.cpp
+++ b/src/lib/state.cpp
@@ -63,11 +63,6 @@
     m_contextStack.pop_back();
 }
 
-Context* StateData::initialContext() const
-{
-    return isEmpty() ? nullptr : m_contextStack.first().first;
-}
-
 Context* StateData::topContext() const
 {
     Q_ASSERT(!isEmpty());
@@ -102,7 +97,7 @@
 
 bool State::operator==(const State &other) const
 {
-    return d->m_contextStack == other.d->m_contextStack;
+    return d->m_contextStack == other.d->m_contextStack && d->m_defData == other.d->m_defData;
 }
 
 bool State::operator!=(const State &other) const
diff --git a/src/lib/state_p.h b/src/lib/state_p.h
--- a/src/lib/state_p.h
+++ b/src/lib/state_p.h
@@ -51,11 +51,18 @@
     int size() const;
     void push(Context *context, const QStringList &captures);
     void pop();
-    Context* initialContext() const;
     Context* topContext() const;
     const QStringList &topCaptures() const;
 
+    /**
+     * definition pointer to check for invalid states
+     * FIXME: this is a hack, one could get the same pointer
+     * later for other object
+     */
+    DefinitionData *m_defData = nullptr;
+
 private:
+
     /**
      * the context stack combines the active context + valid captures
      */