diff --git a/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/middleware/params.clj b/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/middleware/params.clj
index 2b282e8ac..234fab567 100644
--- a/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/middleware/params.clj
+++ b/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/middleware/params.clj
@@ -13,6 +13,10 @@
   (format "Invalid parameter `%s` with value `%s`. Should be a date in format YYYY, YYYY-MM or YYYY-MM-DD."
           name value))
 
+(defn- invalid-string-param-msg [name value]
+  (format "Invalid parameter `%s` with value `%s`. Should be a string."
+          name value))
+
 (defn- get-param-value-from-resource [body name]
   (when (identical? :fhir/Parameters (fhir-spec/fhir-type body))
     (some #(when (= name (:name %)) (:value %)) (:parameter body))))
@@ -57,6 +61,14 @@
    :fhir/operation-outcome "MSG_PARAM_INVALID"
    :fhir.issue/expression name))
 
+(defn- invalid-string-param-anom
+  [name value]
+  (ba/incorrect
+   (invalid-string-param-msg name value)
+   :fhir/issue "value"
+   :fhir/operation-outcome "MSG_PARAM_INVALID"
+   :fhir.issue/expression name))
+
 (defn- coerce-date
   "Coerces `value` into a System.Date.
 
@@ -70,6 +82,9 @@
 (defn- validate-date [name value]
   (if (system/date? value) value (invalid-date-param-anom name value)))
 
+(defn- validate-string [name value]
+  (if (string? value) value (invalid-string-param-anom name value)))
+
 (defn- invalid-report-type-param-msg [report-type]
   (format "Invalid parameter `reportType` with value `%s`. Should be one of `subject`, `subject-list` or `population`."
           report-type))
@@ -105,9 +120,9 @@
             period-end (get-required-param-value
                         request "periodEnd" coerce-date validate-date)
             measure (get-param-value
-                     request "measure" (fn [_n v] v))
+                     request "measure" (fn [_n v] v) validate-string)
             report-type (get-param-value
-                         request "reportType" coerce-report-type)
+                         request "reportType" coerce-report-type validate-string)
             subject-ref (coerce-subject-ref-param request)]
     (let [report-type (some-> report-type type/value)]
       (if (and (= :get request-method) (= "subject-list" report-type))