diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index 942d7be..35e9221 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -20,11 +20,11 @@ jobs:
       matrix:
         config:
           -
-            display_name: "WATCOM 1.9"
+            display_name: "WATCOM 2.0"
             runner: "ubuntu-22.04"
             shell: "bash"
 #            compiler_name: ""
-            watcom_version: "1.9"
+            watcom_version: "2.0"
             cmake_preset: "ci-watcom"
 #            build_suffix:
 
@@ -35,6 +35,7 @@ jobs:
       - uses: open-watcom/setup-watcom@v0
         with:
           version: ${{ matrix.config.watcom_version }}
+          tag: last
 
       - uses: actions/checkout@v4
         with:
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 8a41d7e..fbe267d 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -90,6 +90,11 @@ target_link_libraries(rusdoom PRIVATE
     audio_lib
 )
 
+set_target_properties(rusdoom PROPERTIES
+    C_STANDARD 99
+    C_STANDARD_REQUIRED ON
+)
+
 install(TARGETS rusdoom RUNTIME
     DESTINATION .
     PERMISSIONS OWNER_READ OWNER_WRITE OWNER_EXECUTE GROUP_READ GROUP_EXECUTE WORLD_READ WORLD_EXECUTE
diff --git a/src/p_setup.c b/src/p_setup.c
index 87a1739..e737479 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -19,6 +19,7 @@
 //	set up initial state and misc. LUTs.
 //
 
+#include <limits.h>
 #include <stdint.h>
 #include <stdlib.h>
 #include <math.h>