diff --git a/src/autocomplete.d b/src/autocomplete.d
index d0e4941..9c610d4 100644
--- a/src/autocomplete.d
+++ b/src/autocomplete.d
@@ -229,10 +229,13 @@ AutocompleteResponse dotCompletion(T)(T beforeTokens,
 		// responses when the cursor is in the middle of an identifier instead
 		// of at the end
 		auto t = beforeTokens[$ - 1];
-		partial = t.text[0 .. cursorPosition - t.index];
+		if (cursorPosition - t.index >= 0 && cursorPosition - t.index < t.text.length)
+		{
+			partial = t.text[0 .. cursorPosition - t.index];
 
-		significantTokenType = tok!"identifier";
-		beforeTokens = beforeTokens[0 .. $ - 1];
+			significantTokenType = tok!"identifier";
+			beforeTokens = beforeTokens[0 .. $ - 1];
+		}
 	}
 	else if (beforeTokens.length >= 2 && beforeTokens[$ - 1] ==  tok!".")
 		significantTokenType = beforeTokens[$ - 2].type;