diff --git a/.github/workflows/build-on-pull-request.yml b/.github/workflows/build-on-pull-request.yml
index f5477d191..4408727b3 100644
--- a/.github/workflows/build-on-pull-request.yml
+++ b/.github/workflows/build-on-pull-request.yml
@@ -33,6 +33,71 @@ jobs:
       - name: Test that the samples can be built.
         shell: bash
         run: make -j2 samples
+      - name: Test that the targettest programs can be built.
+        shell: bash
+        run: |
+            make SYS=apple2 -C targettest
+            make SYS=apple2 -C targettest clean
+            make SYS=apple2enh -C targettest
+            make SYS=apple2enh -C targettest clean
+            make SYS=atari -C targettest
+            make SYS=atari -C targettest clean
+            make SYS=atarixl -C targettest
+            make SYS=atarixl -C targettest clean
+            make SYS=atari2600 -C targettest
+            make SYS=atari2600 -C targettest clean
+            make SYS=atari5200 -C targettest
+            make SYS=atari5200 -C targettest clean
+            make SYS=atmos -C targettest
+            make SYS=atmos -C targettest clean
+            make SYS=bbc -C targettest
+            make SYS=bbc -C targettest clean
+            make SYS=c128 -C targettest
+            make SYS=c128 -C targettest clean
+            make SYS=c16 -C targettest
+            make SYS=c16 -C targettest clean
+            make SYS=c64 -C targettest
+            make SYS=c64 -C targettest clean
+            make SYS=cbm510 -C targettest
+            make SYS=cbm510 -C targettest clean
+            make SYS=cbm610 -C targettest
+            make SYS=cbm610 -C targettest clean
+            make SYS=creativision -C targettest
+            make SYS=creativision -C targettest clean
+            make SYS=cx16 -C targettest
+            make SYS=cx16 -C targettest clean
+            make SYS=gamate -C targettest
+            make SYS=gamate -C targettest clean
+            make SYS=geos-apple -C targettest
+            make SYS=geos-apple -C targettest clean
+            make SYS=geos-cbm -C targettest
+            make SYS=geos-cbm -C targettest clean
+            make SYS=lunix -C targettest
+            make SYS=lunix -C targettest clean
+            make SYS=lynx -C targettest
+            make SYS=lynx -C targettest clean
+            make SYS=nes -C targettest
+            make SYS=nes -C targettest clean
+            make SYS=osic1p -C targettest
+            make SYS=osic1p -C targettest clean
+            make SYS=pce -C targettest
+            make SYS=pce -C targettest clean
+            make SYS=pet -C targettest
+            make SYS=pet -C targettest clean
+            make SYS=plus4 -C targettest
+            make SYS=plus4 -C targettest clean
+            make SYS=sim6502 -C targettest
+            make SYS=sim6502 -C targettest clean
+            make SYS=sim65c02 -C targettest
+            make SYS=sim65c02 -C targettest clean
+            make SYS=supervision -C targettest
+            make SYS=supervision -C targettest clean
+            make SYS=sym1 -C targettest
+            make SYS=sym1 -C targettest clean
+            make SYS=telestrat -C targettest
+            make SYS=telestrat -C targettest clean
+            make SYS=vic20 -C targettest
+            make SYS=vic20 -C targettest clean
       - name: Build the document files.
         shell: bash
         run: make -j2 doc