diff --git a/projects/libpng-proto/Dockerfile b/projects/libpng-proto/Dockerfile
index 4438b0b3f..e6952d3c9 100644
--- a/projects/libpng-proto/Dockerfile
+++ b/projects/libpng-proto/Dockerfile
@@ -21,5 +21,5 @@ RUN apt-get update && \
 
 RUN git clone --depth 1 https://github.com/glennrp/libpng.git
 RUN git clone --depth 1 https://github.com/google/libprotobuf-mutator.git
-RUN (mkdir LPM && cd LPM && cmake ../libprotobuf-mutator -GNinja -DLIB_PROTO_MUTATOR_DOWNLOAD_PROTOBUF=ON -DLIB_PROTO_MUTATOR_TESTING=OFF && ninja)
+RUN (mkdir LPM && cd LPM && cmake ../libprotobuf-mutator -GNinja -DLIB_PROTO_MUTATOR_DOWNLOAD_PROTOBUF=ON -DLIB_PROTO_MUTATOR_TESTING=OFF -DCMAKE_BUILD_TYPE=Release && ninja)
 COPY build.sh png_fuzz_proto.proto  png_proto_fuzzer_example.cc $SRC/