diff --git a/lib/rake/task.rb b/lib/rake/task.rb
index 1d3244d2b..5300b6fc4 100644
--- a/lib/rake/task.rb
+++ b/lib/rake/task.rb
@@ -304,10 +304,10 @@ def transform_comments(separator, &block)
     private :transform_comments
 
     # Get the first sentence in a string. The sentence is terminated
-    # by the first period or the end of the line. Decimal points do
-    # not count as periods.
+    # by the first period, exclamation mark, or the end of the line.
+    # Decimal points do not count as periods.
     def first_sentence(string)
-      string.split(/\.[ \t]|\.$|\n/).first
+      string.split(/(?<=\w)(\.|!)[ \t]|(\.$|!)|\n/).first
     end
     private :first_sentence