diff --git a/app/controllers/api/attachments_controller.rb b/app/controllers/api/attachments_controller.rb
index eacabbd6..37e827b5 100644
--- a/app/controllers/api/attachments_controller.rb
+++ b/app/controllers/api/attachments_controller.rb
@@ -10,6 +10,12 @@ module Api
     def create
       submitter = Submitter.find_by!(slug: params[:submitter_slug])
 
+      if params[:type].in?(%w[initials signature]) && ImageUtils.blank?(Vips::Image.new_from_file(params[:file].path))
+        Rollbar.error("Empty signature: #{submitter.id}") if defined?(Rollbar)
+
+        return render json: { error: "#{params[:type]} is empty" }, status: :unprocessable_entity
+      end
+
       attachment = Submitters.create_attachment!(submitter, params)
 
       if params[:remember_signature] == 'true' && submitter.email.present?
diff --git a/app/javascript/submission_form/initials_step.vue b/app/javascript/submission_form/initials_step.vue
index 531b9784..fe36db8f 100644
--- a/app/javascript/submission_form/initials_step.vue
+++ b/app/javascript/submission_form/initials_step.vue
@@ -362,11 +362,20 @@ export default {
             formData.append('file', file)
             formData.append('submitter_slug', this.submitterSlug)
             formData.append('name', 'attachments')
+            formData.append('type', 'initials')
 
             return fetch(this.baseUrl + '/api/attachments', {
               method: 'POST',
               body: formData
-            }).then((resp) => resp.json()).then((attachment) => {
+            }).then(async (resp) => {
+              if (resp.status === 422 || resp.status === 500) {
+                const data = await resp.json()
+
+                return Promise.reject(new Error(data.error))
+              }
+
+              const attachment = await resp.json()
+
               this.$emit('attached', attachment)
               this.$emit('update:model-value', attachment.uuid)
 
diff --git a/app/javascript/submission_form/signature_step.vue b/app/javascript/submission_form/signature_step.vue
index 2011b77a..0b09e8cf 100644
--- a/app/javascript/submission_form/signature_step.vue
+++ b/app/javascript/submission_form/signature_step.vue
@@ -716,11 +716,20 @@ export default {
             formData.append('submitter_slug', this.submitterSlug)
             formData.append('name', 'attachments')
             formData.append('remember_signature', this.rememberSignature)
+            formData.append('type', 'signature')
 
             return fetch(this.baseUrl + '/api/attachments', {
               method: 'POST',
               body: formData
-            }).then((resp) => resp.json()).then((attachment) => {
+            }).then(async (resp) => {
+              if (resp.status === 422 || resp.status === 500) {
+                const data = await resp.json()
+
+                return Promise.reject(new Error(data.error))
+              }
+
+              const attachment = await resp.json()
+
               this.$emit('attached', attachment)
               this.$emit('update:model-value', attachment.uuid)
 
diff --git a/lib/image_utils.rb b/lib/image_utils.rb
index 18f99ad5..57f630a5 100644
--- a/lib/image_utils.rb
+++ b/lib/image_utils.rb
@@ -9,7 +9,6 @@ module ImageUtils
 
     return true if min.all?(255) && max.all?(255)
     return true if min.all?(0) && max.all?(0)
-    return true if min.length >= 4 && min[-1].zero? && max[-1].zero?
 
     false
   end