diff --git a/.travis.yml b/.travis.yml
index 1892da779..86e197b6c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -22,14 +22,15 @@ env:
     # amount of time to execute compared to the optimized builds.
 
     # clang
-    - LINUX_BASE=ubuntu_18.04 C_COMPILER=clang CXX_COMPILER=clang++ TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Debug UBSAN_BUILD=1 RUN_UNIT_TESTS=BUILD_ONLY
-    - LINUX_BASE=ubuntu_18.04 C_COMPILER=clang CXX_COMPILER=clang++ TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Debug ASAN_BUILD=1 RUN_UNIT_TESTS=BUILD_ONLY
+    - LINUX_BASE=ubuntu_18.04 C_COMPILER=clang CXX_COMPILER=clang++ TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Debug UBSAN_BUILD=1 RUN_UNIT_TESTS=BUILD_AND_RUN
+    - LINUX_BASE=ubuntu_18.04 C_COMPILER=clang CXX_COMPILER=clang++ TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Debug ASAN_BUILD=1 RUN_UNIT_TESTS=BUILD_AND_RUN
     - LINUX_BASE=ubuntu_18.04 C_COMPILER=clang CXX_COMPILER=clang++ TARGET_ARCH=x86_64 Z3_BUILD_TYPE=RelWithDebInfo ASAN_BUILD=1 RUN_UNIT_TESTS=BUILD_AND_RUN UBSAN_BUILD=1 RUN_API_EXAMPLES=0 RUN_SYSTEM_TESTS=0 DOTNET_BINDINGS=0 JAVA_BINDINGS=0 PYTHON_BINDINGS=0
 
     # gcc
     - LINUX_BASE=ubuntu_18.04 C_COMPILER=gcc CXX_COMPILER=g++ TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Release RUN_UNIT_TESTS=BUILD_AND_RUN
-    - LINUX_BASE=ubuntu_18.04 C_COMPILER=gcc CXX_COMPILER=g++ TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Debug UBSAN_BUILD=1 RUN_UNIT_TESTS=BUILD_ONLY
-    - LINUX_BASE=ubuntu_18.04 C_COMPILER=gcc CXX_COMPILER=g++ TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Debug ASAN_BUILD=1 RUN_UNIT_TESTS=BUILD_ONLY
+    - LINUX_BASE=ubuntu_18.04 C_COMPILER=gcc CXX_COMPILER=g++ TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Debug UBSAN_BUILD=1 RUN_UNIT_TESTS=BUILD_AND_RUN
+    # 18.04's gcc asan lib doesn't support pthread_atfork. TODO: enable for ubuntu 20.04
+    #- LINUX_BASE=ubuntu_18.04 C_COMPILER=gcc CXX_COMPILER=g++ TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Debug ASAN_BUILD=1 RUN_UNIT_TESTS=BUILD_AND_RUN
 
     # Both of the two configurations below build the docs because the current
     # implementation uses python as part of the building process.