diff --git a/0.21/Dockerfile b/0.21/Dockerfile
index a22d964..df70012 100644
--- a/0.21/Dockerfile
+++ b/0.21/Dockerfile
@@ -156,6 +156,7 @@ RUN ./autogen.sh
 
 # TODO: Try to optimize on passed params
 RUN ./configure LDFLAGS=-L/opt/db4/lib/ CPPFLAGS=-I/opt/db4/include/ \
+    CXXFLAGS="-O2" \
     --prefix="$BITCOIN_PREFIX" \
     --disable-man \
     --disable-shared \