diff --git a/src/editorsupport.ts b/src/editorsupport.ts
index 4385988..09d768f 100644
--- a/src/editorsupport.ts
+++ b/src/editorsupport.ts
@@ -8,16 +8,20 @@ export class BlockDetector {
         const position = this.editor.selection.active;
         const doc = this.editor.document;
 
-        let startLine = doc.lineAt(position.line-1);
-        let endLine = doc.lineAt(position.line);
-
-        while (!startLine.isEmptyOrWhitespace && startLine.lineNumber > 0) {
-            startLine = doc.lineAt(startLine.lineNumber-1)
-        }
-        if (startLine.isEmptyOrWhitespace) {
-            startLine = doc.lineAt(startLine.lineNumber+1)
+        let startLine = null;
+        if (position.line == 0) {
+            startLine = doc.lineAt(position.line);
+        } else {
+            startLine = doc.lineAt(position.line-1);
+            while (!startLine.isEmptyOrWhitespace && startLine.lineNumber > 0) {
+                startLine = doc.lineAt(startLine.lineNumber-1)
+            }
+            if (startLine.isEmptyOrWhitespace) {
+                startLine = doc.lineAt(startLine.lineNumber+1)
+            }
         }
 
+        let endLine = doc.lineAt(position.line);
         let createMatch = startLine.text.match(/create\s+(or\s+replace\s+)?(\w+)\s+(\S+)/)
         if (createMatch) {
             while (!endLine.text.match("end " + createMatch[3] + ";") && endLine.lineNumber < doc.lineCount-1) {