diff --git a/biojava-structure/src/main/java/org/biojava/nbio/structure/io/PDBFileParser.java b/biojava-structure/src/main/java/org/biojava/nbio/structure/io/PDBFileParser.java
index eeac1912ab..06d2cc340a 100644
--- a/biojava-structure/src/main/java/org/biojava/nbio/structure/io/PDBFileParser.java
+++ b/biojava-structure/src/main/java/org/biojava/nbio/structure/io/PDBFileParser.java
@@ -2002,7 +2002,7 @@ private void switchCAOnly(){
 
 	/** safes repeating a few lines ... */
 	private Integer conect_helper (String line,int start,int end) {
-		if (line.length() < end) return null;
+		if (line.length() < start || line.length() < end) return null;
 
 		String sbond = line.substring(start,end).trim();
 		int bond  = -1 ;
@@ -3651,4 +3651,4 @@ public FileParsingParameters getFileParsingParameters(){
 	}
 
 
-}
\ No newline at end of file
+}