diff --git a/src/peghighlighterresult.cpp b/src/peghighlighterresult.cpp
index d7da5a5a..51594f3a 100644
--- a/src/peghighlighterresult.cpp
+++ b/src/peghighlighterresult.cpp
@@ -119,7 +119,7 @@ void PegHighlighterResult::parseBlocksHighlightOne(QVector<QVector<HLUnit>> &p_b
 
     QTextBlock block = p_doc->findBlock(p_pos);
     int startBlockNum = block.blockNumber();
-    int endBlockNum = p_doc->findBlock(p_end).blockNumber();
+    int endBlockNum = p_doc->findBlock(p_end - 1).blockNumber();
     if (endBlockNum >= p_blocksHighlights.size()) {
         endBlockNum = p_blocksHighlights.size() - 1;
     }
@@ -144,9 +144,14 @@ void PegHighlighterResult::parseBlocksHighlightOne(QVector<QVector<HLUnit>> &p_b
             unit.start = 0;
             unit.length = block.length();
         }
+
         unit.styleIndex = p_styleIndex;
 
-        p_blocksHighlights[blockNum].append(unit);
+        Q_ASSERT(unit.length > 0);
+
+        if (unit.length > 0) {
+            p_blocksHighlights[blockNum].append(unit);
+        }
 
         block = block.next();
     }
@@ -167,7 +172,11 @@ void PegHighlighterResult::parseBlocksElementRegionOne(QHash<int, QVector<VEleme
 
     QTextBlock block = p_doc->findBlock(p_pos);
     int startBlockNum = block.blockNumber();
-    int endBlockNum = p_doc->findBlock(p_end).blockNumber();
+    int endBlockNum = p_doc->findBlock(p_end - 1).blockNumber();
+    if (endBlockNum >= p_regs.size()) {
+        endBlockNum = p_regs.size() - 1;
+    }
+
     while (block.isValid())
     {
         int blockNum = block.blockNumber();
diff --git a/src/pegmarkdownhighlighter.cpp b/src/pegmarkdownhighlighter.cpp
index c53667d4..8be19255 100644
--- a/src/pegmarkdownhighlighter.cpp
+++ b/src/pegmarkdownhighlighter.cpp
@@ -92,9 +92,9 @@ void PegMarkdownHighlighter::highlightBlock(const QString &p_text)
     int blockNum = block.blockNumber();
 
     if (result->matched(m_timeStamp)) {
-        preHighlightMonospaceBlock(result->m_blocksHighlights, blockNum, p_text);
+        preHighlightSingleFormatBlock(result->m_blocksHighlights, blockNum, p_text);
     } else {
-        preHighlightMonospaceBlock(m_fastResult->m_blocksHighlights, blockNum, p_text);
+        preHighlightSingleFormatBlock(m_fastResult->m_blocksHighlights, blockNum, p_text);
     }
 
     highlightBlockOne(result->m_blocksHighlights, blockNum);
@@ -116,9 +116,9 @@ void PegMarkdownHighlighter::highlightBlock(const QString &p_text)
     }
 }
 
-void PegMarkdownHighlighter::preHighlightMonospaceBlock(const QVector<QVector<HLUnit>> &p_highlights,
-                                                        int p_blockNum,
-                                                        const QString &p_text)
+void PegMarkdownHighlighter::preHighlightSingleFormatBlock(const QVector<QVector<HLUnit>> &p_highlights,
+                                                           int p_blockNum,
+                                                           const QString &p_text)
 {
     int sz = p_text.size();
     if (sz == 0) {
@@ -210,7 +210,7 @@ void PegMarkdownHighlighter::startFastParse(int p_position, int p_charsRemoved,
     int firstBlockNum, lastBlockNum;
     getFastParseBlockRange(p_position, p_charsRemoved, p_charsAdded, firstBlockNum, lastBlockNum);
     if (firstBlockNum == -1) {
-        m_fastResult.reset();
+        // We could not let m_fastResult NULL here.
         return;
     }
 
@@ -378,7 +378,7 @@ void PegMarkdownHighlighter::updateSingleFormatBlocks(const QVector<QVector<HLUn
             const HLUnit &unit = units[0];
             if (unit.start == 0 && unit.length > 0) {
                 QTextBlock block = m_doc->findBlockByNumber(i);
-                if (block.length() - 1 == (int)unit.length) {
+                if (block.length() - 1 <= (int)unit.length) {
                     m_singleFormatBlocks.insert(i);
                 }
             }
diff --git a/src/pegmarkdownhighlighter.h b/src/pegmarkdownhighlighter.h
index 3ec1e6cf..d2461a99 100644
--- a/src/pegmarkdownhighlighter.h
+++ b/src/pegmarkdownhighlighter.h
@@ -113,9 +113,9 @@ private:
                            int p_blockNum);
 
     // To avoid line height jitter.
-    void preHighlightMonospaceBlock(const QVector<QVector<HLUnit>> &p_highlights,
-                                    int p_blockNum,
-                                    const QString &p_text);
+    void preHighlightSingleFormatBlock(const QVector<QVector<HLUnit>> &p_highlights,
+                                       int p_blockNum,
+                                       const QString &p_text);
 
     void updateSingleFormatBlocks(const QVector<QVector<HLUnit>> &p_highlights);