diff --git a/lib/fbe/iterate.rb b/lib/fbe/iterate.rb
index 969d5d3..f72b239 100644
--- a/lib/fbe/iterate.rb
+++ b/lib/fbe/iterate.rb
@@ -97,6 +97,7 @@ def initialize(fb:, loog:, options:, global:, epoch:, kickoff:)
     @kickoff = kickoff
     @label = nil
     @since = 0
+    @custom = false
     @query = nil
     @sorting = nil
     @repeats = 1
@@ -161,9 +162,11 @@ def repeats(repeats)
   # @example Start iteration from issue number 100
   #   iterator.since(100)
   def since(value)
+    raise(Fbe::Error, 'Since is already set') if @custom
     raise(Fbe::Error, 'Cannot set "since" to nil') if value.nil?
     raise(Fbe::Error, 'The "since" must be an Integer') unless value.is_a?(Integer)
     @since = value
+    @custom = true
   end
 
   # Sets the query to execute for each iteration.
diff --git a/test/fbe/test_iterate.rb b/test/fbe/test_iterate.rb
index dc9cfd0..0d4b244 100644
--- a/test/fbe/test_iterate.rb
+++ b/test/fbe/test_iterate.rb
@@ -191,6 +191,54 @@ def test_raises_when_repeats_is_not_positive
     end
   end
 
+  def test_configures_since_start
+    opts = Judges::Options.new(['repositories=foo/bar', 'testing=true'])
+    fb = Fbe.fb(fb: Factbase.new, global: {}, options: opts, loog: Loog::NULL)
+    seen = []
+    Fbe.iterate(fb:, loog: Loog::NULL, global: {}, options: opts, epoch: Time.now, kickoff: Time.now) do
+      as('custom_since_test')
+      since(7)
+      by('(plus $before 1)')
+      repeats(1)
+      over do |_, nxt|
+        seen << nxt
+        nxt
+      end
+    end
+    assert_equal([8], seen)
+  end
+
+  def test_raises_when_since_is_nil
+    opts = Judges::Options.new(['repositories=foo/bar', 'testing=true'])
+    fb = Fbe.fb(fb: Factbase.new, global: {}, options: opts, loog: Loog::NULL)
+    assert_raises(Fbe::Error) do
+      Fbe.iterate(fb:, loog: Loog::NULL, global: {}, options: opts, epoch: Time.now, kickoff: Time.now) do
+        since(nil)
+      end
+    end
+  end
+
+  def test_raises_when_since_is_not_integer
+    opts = Judges::Options.new(['repositories=foo/bar', 'testing=true'])
+    fb = Fbe.fb(fb: Factbase.new, global: {}, options: opts, loog: Loog::NULL)
+    assert_raises(Fbe::Error) do
+      Fbe.iterate(fb:, loog: Loog::NULL, global: {}, options: opts, epoch: Time.now, kickoff: Time.now) do
+        since('7')
+      end
+    end
+  end
+
+  def test_raises_when_since_set_twice
+    opts = Judges::Options.new(['repositories=foo/bar', 'testing=true'])
+    fb = Fbe.fb(fb: Factbase.new, global: {}, options: opts, loog: Loog::NULL)
+    assert_raises(Fbe::Error) do
+      Fbe.iterate(fb:, loog: Loog::NULL, global: {}, options: opts, epoch: Time.now, kickoff: Time.now) do
+        since(1)
+        since(2)
+      end
+    end
+  end
+
   def test_raises_when_label_is_nil
     opts = Judges::Options.new(['repositories=foo/bar', 'testing=true'])
     fb = Fbe.fb(fb: Factbase.new, global: {}, options: opts, loog: Loog::NULL)