diff --git a/.ci-pipelines/build-matrix.yml b/.ci-pipelines/build-matrix.yml
index f907c5fb4..b0924767c 100644
--- a/.ci-pipelines/build-matrix.yml
+++ b/.ci-pipelines/build-matrix.yml
@@ -28,12 +28,6 @@ pool:
 # Define the "matrix" of build images to try building GEOS-Chem in
 strategy:
   matrix:
-    ubuntu_gcc4:
-      GCC_VERSION: 4
-      containerImage: liambindle/penelope:0.1.0-ubuntu16.04-gcc4-netcdf4.5.0-netcdff4.4.4
-    ubuntu_gcc5:
-      GCC_VERSION: 5
-      containerImage: liambindle/penelope:0.1.0-ubuntu16.04-gcc5-netcdf4.5.0-netcdff4.4.4
     ubuntu_gcc6:
       GCC_VERSION: 6
       containerImage: liambindle/penelope:0.1.0-ubuntu16.04-gcc6-netcdf4.5.0-netcdff4.4.4
@@ -52,9 +46,6 @@ strategy:
     ubuntu_netcdf_old:
       GCC_VERSION: 9
       containerImage: liambindle/penelope:0.1.0-ubuntu16.04-netcdf4.1.3
-    centos_gcc4:
-      GCC_VERSION: 4
-      containerImage: liambindle/penelope:0.1.0-centos7-gcc4-netcdf4.5.0-netcdff4.4.4
     centos_gcc7:
       GCC_VERSION: 7
       containerImage: liambindle/penelope:0.1.0-centos7-gcc7-netcdf4.5.0-netcdff4.4.4