diff --git a/main/mio.c b/main/mio.c
index baabcf5bff..a5c9c7bdf7 100644
--- a/main/mio.c
+++ b/main/mio.c
@@ -317,6 +317,9 @@ MIO *mio_new_mio (MIO *base, long start, long size)
 	MIO *submio;
 	size_t r;
 
+	if (start < 0 || size < -1)
+		return NULL;
+
 	original_pos = mio_tell (base);
 
 	if (size == -1)
diff --git a/main/parse.c b/main/parse.c
index 201004c7fb..11d40af150 100644
--- a/main/parse.c
+++ b/main/parse.c
@@ -4322,7 +4322,7 @@ extern bool runParserInArea (const langType language,
 							 unsigned long sourceLineOffset,
 							 int promise)
 {
-	bool tagFileResized;
+	bool tagFileResized = false;
 
 	verbose ("runParserInArea: %s; "
 			 "file: %s, "
@@ -4334,13 +4334,15 @@ extern bool runParserInArea (const langType language,
 			 startLine, startCharOffset, sourceLineOffset,
 			 endLine, endCharOffset);
 
-	pushArea (doesParserRequireMemoryStream (language),
+	if (pushArea (doesParserRequireMemoryStream (language),
 			  startLine, startCharOffset,
 			  endLine, endCharOffset,
 			  sourceLineOffset,
-			  promise);
-	tagFileResized = createTagsWithFallback1 (language, NULL);
-	popArea  ();
+			  promise))
+	{
+		tagFileResized = createTagsWithFallback1 (language, NULL);
+		popArea  ();
+	}
 	return tagFileResized;
 
 }
diff --git a/main/read.c b/main/read.c
index 2118ec1e99..fe5d8c99c2 100644
--- a/main/read.c
+++ b/main/read.c
@@ -1394,7 +1394,7 @@ extern char *readLineFromBypass (
 	return data.result;
 }
 
-extern void   pushArea (
+extern bool   pushArea (
 				       bool useMemoryStreamInput,
 				       unsigned long startLine, long startColumn,
 				       unsigned long endLine, long endColumn,
@@ -1415,7 +1415,7 @@ extern void   pushArea (
 		{
 			File.thinDepth++;
 			verbose ("push thin area (%d)\n", File.thinDepth);
-			return;
+			return true;
 		}
 		error(WARNING, "INTERNAL ERROR: though pushing MEMORY based thin area, "
 			  "underlying area is a FILE base: %s@%s",
@@ -1427,12 +1427,15 @@ extern void   pushArea (
 	original = getInputFilePosition ();
 
 	tmp = getInputFilePositionForLine (startLine);
-	mio_setpos (File.mio, &tmp);
-	mio_seek (File.mio, startColumn, SEEK_CUR);
+	if (mio_setpos (File.mio, &tmp) != 0)
+		goto fail;
+	if (mio_seek (File.mio, startColumn, SEEK_CUR) != 0)
+		goto fail;
 	p = mio_tell (File.mio);
 
 	tmp = getInputFilePositionForLine (endLine);
-	mio_setpos (File.mio, &tmp);
+	if (mio_setpos (File.mio, &tmp) != 0)
+		goto fail;
 	if (endColumn == EOL_COLUMN)
 	{
 		long line_start = mio_tell (File.mio);
@@ -1443,9 +1446,15 @@ extern void   pushArea (
 		Assert (endColumn >= 0);
 	}
 	else
-		mio_seek (File.mio, endColumn, SEEK_CUR);
+	{
+		if (mio_seek (File.mio, endColumn, SEEK_CUR) != 0)
+			goto fail;
+	}
 	q = mio_tell (File.mio);
 
+	if (q <= p)
+		goto fail;
+
 	mio_setpos (File.mio, &original);
 
 	invalidatePatternCache();
@@ -1473,6 +1482,12 @@ extern void   pushArea (
 
 	File.input.lineNumberOrigin = ((startLine == 0)? 0: startLine - 1);
 	File.source.lineNumberOrigin = ((sourceLineOffset == 0)? 0: sourceLineOffset - 1);
+
+	return true;
+
+fail:
+	mio_setpos (File.mio, &original);
+	return false;
 }
 
 extern bool isAreaStacked (void)
diff --git a/main/read_p.h b/main/read_p.h
index cdfa18b4ae..446599c14c 100644
--- a/main/read_p.h
+++ b/main/read_p.h
@@ -82,7 +82,7 @@ extern char *readLineFromBypass (vString *const vLine, MIOPos pos, long *const o
  * args (endColumn): [absolute]
  * args (sourceLineOffset): [buggy]
  */
-extern void   pushArea (
+extern bool   pushArea (
 				       bool useMemoryStreamInput,
 				       unsigned long startLine, long startColumn,
 				       unsigned long endLine, long endColumn,