diff --git a/Makefile b/Makefile
index 670e4a2635ec..494e3ddb4c8f 100644
--- a/Makefile
+++ b/Makefile
@@ -292,7 +292,7 @@ contribs/dist: .build/build-dll.timestamp
 	mkdir -p $(dir $@)
 	CI=true LANGUAGE=en_US buildtools/retry node buildtools/check-example.js \
 		.build/examples-hosted/$*.html
-	buildtools/check-example .build/examples-hosted/$*.html.png examples/$*-ref.png
+	buildtools/check-example --generate .build/examples-hosted/$*.html.png examples/$*-ref.png
 	touch $@
 
 .build/error.check.timestamp: .build/examples-ngeo.timestamp \
@@ -310,7 +310,7 @@ contribs/dist: .build/build-dll.timestamp
 	mkdir -p $(dir $@)
 	CI=true LANGUAGE=en_US buildtools/retry node buildtools/check-example.js \
 		.build/examples-hosted/contribs/gmf/$*.html
-	buildtools/check-example .build/examples-hosted/contribs/gmf/$*.html.png contribs/gmf/examples/$*-ref.png
+	buildtools/check-example --generate .build/examples-hosted/contribs/gmf/$*.html.png contribs/gmf/examples/$*-ref.png
 	touch $@
 
 .build/contribs/gmf/apps/%.check.timestamp: .build/gmf-apps.timestamp \
@@ -318,7 +318,7 @@ contribs/dist: .build/build-dll.timestamp
 	mkdir -p $(dir $@)
 	CI=true LANGUAGE=en_US buildtools/retry node buildtools/check-example.js \
 		.build/examples-hosted/contribs/gmf/apps/$*.html
-	buildtools/check-example .build/examples-hosted/contribs/gmf/apps/$*.html.png contribs/gmf/apps/$*-ref.png
+	buildtools/check-example --generate .build/examples-hosted/contribs/gmf/apps/$*.html.png contribs/gmf/apps/$*-ref.png
 	touch $@
 
 .build/test-check-example/%.check.timestamp: \
diff --git a/buildtools/check-example b/buildtools/check-example
index 81afe2d4fa63..0b1ad5438dcf 100755
--- a/buildtools/check-example
+++ b/buildtools/check-example
@@ -21,6 +21,7 @@
 # IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
+import argparse
 import os
 import shutil
 import subprocess
@@ -42,6 +43,10 @@ def main():
     Optional mask image (name from Reference image): examples/simple-mask.png
     Generate diff image (name from Generated image): .build/examples-hosted/simple-diff.png
     """
+    parser = argparse.ArgumentParser(description=main.__doc__)
+    parser.add_argument("--generate", action="store_true", help="Regenerate the ref image")
+    args = parser.parse_args()
+
     current = sys.argv[1]
     ref = sys.argv[2]
     mask = ref.replace("-ref", "-mask")
@@ -56,12 +61,10 @@ def main():
         subprocess.run(["gm", "composite", "-compose", "Multiply", old_current, mask, current], check=True)
         subprocess.run(["gm", "composite", "-compose", "Multiply", old_ref, mask, ref], check=True)
 
-    # Set to True to regenerate ref images
-    if False:
-        if "/error-" not in ref:
-            shutil.copyfile(current, old_ref)
-            shutil.copyfile(current, ref)
-            sys.exit(0)
+    if args.generate and "/error-" not in ref:
+        shutil.copyfile(current, old_ref)
+        shutil.copyfile(current, ref)
+        sys.exit(0)
     result = subprocess.run(
         [
             "gm",