diff --git a/src/recur.cpp b/src/recur.cpp
index 3181bed3d..f82e7600a 100644
--- a/src/recur.cpp
+++ b/src/recur.cpp
@@ -251,7 +251,7 @@ Datetime getNextRecurrence (Datetime& current, std::string& period)
            Lexer::isAllDigits (period.substr (1, period.length () - 2)) &&
            period[period.length () - 1] == 'M')
   {
-    int increment = strtol (period.substr (0, period.length () - 1).c_str (), nullptr, 10);
+    int increment = strtol (period.substr (1, period.length () - 2).c_str (), nullptr, 10);
 
     m += increment;
     while (m > 12)