diff --git a/FORMULAS-BACKLOG-AND-FEATURE-IDEAS.md b/FORMULAS-BACKLOG-AND-FEATURE-IDEAS.md
index e1125c210..cfa5beb61 100644
--- a/FORMULAS-BACKLOG-AND-FEATURE-IDEAS.md
+++ b/FORMULAS-BACKLOG-AND-FEATURE-IDEAS.md
@@ -27,9 +27,9 @@
       
 * [x] validate that opt-map is only used with valid keys.
 
-* [ ] validate that :num-trials is 1+
+* [x] validate that :num-trials is 1+
 
-* [ ] more formula syntax valiidation cases inspired by the new opt map
+* [ ] more formula syntax validation cases inspired by the new opt map
   
 * [ ] Work with Meikel Brandmeyer to combine ClojureCheck's Generators with Shrink.
       implement shrinking. Report only the first fully shrunken failure
diff --git a/src/midje/ideas/formulas.clj b/src/midje/ideas/formulas.clj
index 51b8fed62..26a477dec 100644
--- a/src/midje/ideas/formulas.clj
+++ b/src/midje/ideas/formulas.clj
@@ -104,5 +104,9 @@
           (not (empty? invalid-keys))
           (simple-report-validation-error form (format "Invalid keys (%s) in formula's options map. Valid keys are: :num-trials" (join ", " invalid-keys)))
           
+          (and (:num-trials opt-map) 
+               (not (pos? (:num-trials opt-map))))
+          (simple-report-validation-error form (str ":num-trials must be an integer 1 or greater. You tried to set it to: " (:num-trials opt-map)))
+      
           :else 
           args)))
\ No newline at end of file
diff --git a/test/midje/ideas/t_formulas.clj b/test/midje/ideas/t_formulas.clj
index d7bdf44dd..55efe4c77 100644
--- a/test/midje/ideas/t_formulas.clj
+++ b/test/midje/ideas/t_formulas.clj
@@ -48,6 +48,13 @@
 (causes-validation-error #"Invalid keys \(:foo, :bar\) in formula's options map. Valid keys are: :num-trials"
   (formula {:foo 5 :bar 6} [a 1] a => 1))
 
+(each-causes-validation-error #":num-trials must be an integer 1 or greater"
+  (formula {:num-trials 0 } [a 1] a => 1)
+  (formula {:num-trials -1} [a 1] a => 1)
+  (formula {:num-trials -2} [a 1] a => 1)
+  (formula {:num-trials -3} [a 1] a => 1)
+  (formula {:num-trials -4} [a 1] a => 1))
+
 (defn z [x] )
 (causes-validation-error #"background cannot be used inside of formula"
   (formula [a 1]
@@ -61,6 +68,13 @@
   (against-background (h 1) => 5)
   (k a) => 10)
 
+;; :num-trials can be any number 1+
+(formula {:num-trials 1 } [a 1] a => 1)
+(formula {:num-trials 2} [a 1] a => 1)
+(formula {:num-trials 3} [a 1] a => 1)
+(formula {:num-trials 4} [a 1] a => 1)
+(formula {:num-trials 10000} [a 1] a => 1)
+
 
 ;; *num-trials* binding validation