diff --git a/internal/apiform/encoder.go b/internal/apiform/encoder.go
index b92fbd7..0a5bfc8 100644
--- a/internal/apiform/encoder.go
+++ b/internal/apiform/encoder.go
@@ -183,6 +183,18 @@ func (e *encoder) newPrimitiveTypeEncoder(t reflect.Type) encoderFunc {
 func (e *encoder) newArrayTypeEncoder(t reflect.Type) encoderFunc {
 	itemEncoder := e.typeEncoder(t.Elem())
 	keyFn := e.arrayKeyEncoder()
+	if e.arrayFmt == "comma" {
+		return func(key string, v reflect.Value, writer *multipart.Writer) error {
+			if v.Len() == 0 {
+				return nil
+			}
+			elements := make([]string, v.Len())
+			for i := 0; i < v.Len(); i++ {
+				elements[i] = fmt.Sprint(v.Index(i).Interface())
+			}
+			return writer.WriteField(key, strings.Join(elements, ","))
+		}
+	}
 	return func(key string, v reflect.Value, writer *multipart.Writer) error {
 		if keyFn == nil {
 			return fmt.Errorf("apiform: unsupported array format")
diff --git a/scripts/mock b/scripts/mock
index 9ecceca..4931f30 100755
--- a/scripts/mock
+++ b/scripts/mock
@@ -24,7 +24,7 @@ if [ "$1" == "--daemon" ]; then
   # Pre-install the package so the download doesn't eat into the startup timeout
   npm exec --package=@stdy/cli@0.19.7 -- steady --version
 
-  npm exec --package=@stdy/cli@0.19.7 -- steady --host 127.0.0.1 -p 4010 --validator-form-array-format=brackets --validator-query-array-format=brackets --validator-form-object-format=brackets --validator-query-object-format=brackets "$URL" &> .stdy.log &
+  npm exec --package=@stdy/cli@0.19.7 -- steady --host 127.0.0.1 -p 4010 --validator-query-array-format=brackets --validator-form-array-format=brackets --validator-query-object-format=brackets --validator-form-object-format=brackets "$URL" &> .stdy.log &
 
   # Wait for server to come online via health endpoint (max 30s)
   echo -n "Waiting for server"
@@ -48,5 +48,5 @@ if [ "$1" == "--daemon" ]; then
 
   echo
 else
-  npm exec --package=@stdy/cli@0.19.7 -- steady --host 127.0.0.1 -p 4010 --validator-form-array-format=brackets --validator-query-array-format=brackets --validator-form-object-format=brackets --validator-query-object-format=brackets "$URL"
+  npm exec --package=@stdy/cli@0.19.7 -- steady --host 127.0.0.1 -p 4010 --validator-query-array-format=brackets --validator-form-array-format=brackets --validator-query-object-format=brackets --validator-form-object-format=brackets "$URL"
 fi
diff --git a/scripts/test b/scripts/test
index 98f2c08..7f58b2e 100755
--- a/scripts/test
+++ b/scripts/test
@@ -43,7 +43,7 @@ elif ! steady_is_running ; then
   echo -e "To run the server, pass in the path or url of your OpenAPI"
   echo -e "spec to the steady command:"
   echo
-  echo -e "  \$ ${YELLOW}npm exec --package=@stdy/cli@0.19.7 -- steady path/to/your.openapi.yml --host 127.0.0.1 -p 4010 --validator-form-array-format=brackets --validator-query-array-format=brackets --validator-form-object-format=brackets --validator-query-object-format=brackets${NC}"
+  echo -e "  \$ ${YELLOW}npm exec --package=@stdy/cli@0.19.7 -- steady path/to/your.openapi.yml --host 127.0.0.1 -p 4010 --validator-query-array-format=brackets --validator-form-array-format=brackets --validator-query-object-format=brackets --validator-form-object-format=brackets${NC}"
   echo
 
   exit 1