diff --git .github/workflows/linux-build.yml .github/workflows/linux-build.yml
index f97ec631f0..8399be980a 100644
--- .github/workflows/linux-build.yml
+++ .github/workflows/linux-build.yml
@@ -16,7 +16,7 @@ jobs:
       matrix:
         cfgopt:
           - ""
-          - "CFLAGS=-DTCL_NO_DEPRECATED=1"
+          - "CPPFLAGS=-DTCL_NO_DEPRECATED=1"
           - "--disable-shared"
           - "--disable-zipfs"
           - "--enable-symbols"
diff --git .github/workflows/win-build.yml .github/workflows/win-build.yml
index b5ee266641..c352f75143 100644
--- .github/workflows/win-build.yml
+++ .github/workflows/win-build.yml
@@ -66,7 +66,7 @@ jobs:
       matrix:
         cfgopt:
           - ""
-          - "CFLAGS=-DTCL_NO_DEPRECATED=1"
+          - "CPPFLAGS=-DTCL_NO_DEPRECATED=1"
           - "--disable-shared"
           - "--disable-zipfs"
           - "--enable-symbols"
diff --git .travis.yml .travis.yml
index 295ba776a4..37b77b1af0 100644
--- .travis.yml
+++ .travis.yml
@@ -26,7 +26,7 @@ jobs:
       compiler: gcc
       env:
         - BUILD_DIR=unix
-        - CFGOPT="CFLAGS=-DTCL_NO_DEPRECATED=1"
+        - CFGOPT="CPPFLAGS=-DTCL_NO_DEPRECATED=1"
     - name: "Linux/GCC/Static"
       os: linux
       dist: focal
@@ -299,7 +299,7 @@ jobs:
       compiler: gcc
       env:
         - BUILD_DIR=win
-        - CFGOPT="--enable-64bit CFLAGS=-DTCL_NO_DEPRECATED=1"
+        - CFGOPT="--enable-64bit CPPFLAGS=-DTCL_NO_DEPRECATED=1"
       before_install: *makepreinst
     - name: "Windows/GCC/Static"
       os: windows
@@ -334,7 +334,7 @@ jobs:
       compiler: gcc
       env:
         - BUILD_DIR=win
-        - CFGOPT="CFLAGS=-DTCL_NO_DEPRECATED=1"
+        - CFGOPT="CPPFLAGS=-DTCL_NO_DEPRECATED=1"
       before_install: *makepreinst
     - name: "Windows/GCC-x86/Static"
       os: windows
