diff --git a/.circleci/docker/Dockerfile.ubuntu1904 b/.circleci/docker/Dockerfile.ubuntu1904
index 4b7f131de..46b95527b 100644
--- a/.circleci/docker/Dockerfile.ubuntu1904
+++ b/.circleci/docker/Dockerfile.ubuntu1904
@@ -46,16 +46,6 @@ RUN set -ex; \
 
 FROM base AS libraries
 
-# Z3
-RUN set -ex; \
-	git clone --depth=1 --branch="Z3-4.8.5" https://github.com/Z3Prover/z3.git /usr/src/z3; \
-	mkdir /usr/src/z3/build; \
-	cd /usr/src/z3/build; \
-	cmake -DCMAKE_BUILD_TYPE="Release" -DCMAKE_INSTALL_PREFIX="/usr" -G "Ninja" ..; \
-	ninja; \
-	ninja install/strip; \
-	rm -rf /usr/src/z3
-
 # OSSFUZZ: libprotobuf-mutator
 RUN set -ex; \
 	git clone https://github.com/google/libprotobuf-mutator.git \
diff --git a/cmake/toolchains/libfuzzer.cmake b/cmake/toolchains/libfuzzer.cmake
index 86d45d304..c92ef8a9e 100644
--- a/cmake/toolchains/libfuzzer.cmake
+++ b/cmake/toolchains/libfuzzer.cmake
@@ -1,2 +1,2 @@
 # Require libfuzzer specific flags
-set(CMAKE_CXX_FLAGS "-O1 -gline-tables-only -fsanitize=address -fsanitize-address-use-after-scope -fsanitize=fuzzer-no-link -stdlib=libstdc++")
+set(CMAKE_CXX_FLAGS "-O1 -gline-tables-only -fsanitize=address -fsanitize-address-use-after-scope -fsanitize=fuzzer-no-link -stdlib=libstdc++ -fopenmp=libgomp")