diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index dbb4d5d2d3..973516abde 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -685,7 +685,12 @@ jobs:
             fi
           fi
           [ -x ~/venv/bin/activate ] && source ~/venv/bin/activate
-          [[ "${MATRIX_INSTALL_STEPS}" = *'codeset-test'* ]] && export LC_ALL=C
+          if [[ "${MATRIX_INSTALL_STEPS}" = *'codeset-test'* ]]; then
+            locale || true
+            export LC_ALL=C
+            export LC_CTYPE=C
+            export LC_NUMERIC=fr_FR.UTF-8
+          fi
           if [ "${MATRIX_BUILD}" = 'cmake' ]; then
             cmake --build bld --verbose --target "${TEST_TARGET}"
           else
diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index bb1b376b27..b35c9a08c4 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -214,6 +214,7 @@ jobs:
       MATRIX_BUILD: ${{ matrix.build.generate && 'cmake' || 'autotools' }}
       MATRIX_COMPILER: '${{ matrix.compiler }}'
       MATRIX_INSTALL: '${{ matrix.build.install }}'
+      MATRIX_INSTALL_STEPS: '${{ matrix.build.install_steps }}'
       MATRIX_MACOS_VERSION_MIN: '${{ matrix.build.macos-version-min }}'
     strategy:
       fail-fast: false
@@ -381,7 +382,6 @@ jobs:
           MATRIX_CHKPREFILL: '${{ matrix.build.chkprefill }}'
           MATRIX_CONFIGURE: '${{ matrix.build.configure }}'
           MATRIX_GENERATE: '${{ matrix.build.generate }}'
-          MATRIX_INSTALL_STEPS: '${{ matrix.build.install_steps }}'
         run: |
           if [[ "${MATRIX_COMPILER}" = 'gcc'* ]]; then
             sysroot="$("${CC}" --print-sysroot)"  # Must match the SDK gcc was built for
@@ -481,6 +481,8 @@ jobs:
           TFLAGS="-j20 ${TFLAGS}"
           source ~/venv/bin/activate
           if [[ "${MATRIX_INSTALL_STEPS}" = *'codeset-test'* ]]; then
+            locale || true
+            export LC_ALL=C
             export LC_CTYPE=C
             export LC_NUMERIC=fr_FR.UTF-8
           fi
diff --git a/docs/tests/TEST-SUITE.md b/docs/tests/TEST-SUITE.md
index 1e387898f7..2110cfb362 100644
--- a/docs/tests/TEST-SUITE.md
+++ b/docs/tests/TEST-SUITE.md
@@ -53,7 +53,6 @@ SPDX-License-Identifier: curl
   - `openssl` (the command line tool, for generating test server certificates)
   - `openssh` or `SunSSH` (for SCP and SFTP tests)
   - `nghttpx` (for HTTP/2 and HTTP/3 tests)
-  - An available `en_US.UTF-8` locale
 
 ### Installation of impacket
 
diff --git a/tests/data/test1034 b/tests/data/test1034
index ef671dfe2e..eda13bb23e 100644
--- a/tests/data/test1034
+++ b/tests/data/test1034
@@ -29,8 +29,7 @@ proxy
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 HTTP over proxy with malformatted IDN host name
diff --git a/tests/data/test1035 b/tests/data/test1035
index b6f30ae56b..c8eb282aff 100644
--- a/tests/data/test1035
+++ b/tests/data/test1035
@@ -27,8 +27,7 @@ proxy
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 HTTP over proxy with too long IDN host name
diff --git a/tests/data/test1448 b/tests/data/test1448
index 96d64b85a5..f7ff09f952 100644
--- a/tests/data/test1448
+++ b/tests/data/test1448
@@ -43,8 +43,7 @@ IDN
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 Redirect following to UTF-8 IDN host name
diff --git a/tests/data/test1560 b/tests/data/test1560
index 976cc98ec2..ce8c7c42a7 100644
--- a/tests/data/test1560
+++ b/tests/data/test1560
@@ -13,7 +13,7 @@ urlapi
 none
 </server>
 <setenv>
-LC_ALL=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <features>
 file
diff --git a/tests/data/test165 b/tests/data/test165
index 0b5cfd2346..4996a3564f 100644
--- a/tests/data/test165
+++ b/tests/data/test165
@@ -33,8 +33,7 @@ proxy
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 HTTP over proxy with IDN host name
diff --git a/tests/data/test2046 b/tests/data/test2046
index cf25d0c57b..555515aa4a 100644
--- a/tests/data/test2046
+++ b/tests/data/test2046
@@ -43,8 +43,7 @@ IDN
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 Connection reuse with IDN host name
diff --git a/tests/data/test2047 b/tests/data/test2047
index c32e6aabc7..9c671b1785 100644
--- a/tests/data/test2047
+++ b/tests/data/test2047
@@ -44,8 +44,7 @@ proxy
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 Connection reuse with IDN host name over HTTP proxy
diff --git a/tests/data/test955 b/tests/data/test955
index 817b47a67e..633c2e369d 100644
--- a/tests/data/test955
+++ b/tests/data/test955
@@ -24,8 +24,7 @@ smtp
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP without SMTPUTF8 support - UTF-8 based sender (local part only)
diff --git a/tests/data/test956 b/tests/data/test956
index 4546f2ee61..9472e96e15 100644
--- a/tests/data/test956
+++ b/tests/data/test956
@@ -21,8 +21,7 @@ smtp
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP without SMTPUTF8 support - UTF-8 based recipient (local part only)
diff --git a/tests/data/test957 b/tests/data/test957
index 9548627b98..671d73bbf2 100644
--- a/tests/data/test957
+++ b/tests/data/test957
@@ -22,8 +22,7 @@ smtp
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP VRFY without SMTPUTF8 support - UTF-8 recipient (local part only)
diff --git a/tests/data/test958 b/tests/data/test958
index f1006a0a66..203254bfc2 100644
--- a/tests/data/test958
+++ b/tests/data/test958
@@ -22,8 +22,7 @@ smtp
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP external VRFY without SMTPUTF8 - UTF-8 recipient (local part only)
diff --git a/tests/data/test959 b/tests/data/test959
index 2154600da2..5693e34944 100644
--- a/tests/data/test959
+++ b/tests/data/test959
@@ -25,8 +25,7 @@ smtp
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP without SMTPUTF8 support - UTF-8 based sender (host part only)
diff --git a/tests/data/test960 b/tests/data/test960
index fb50a326b2..ced2ba0b54 100644
--- a/tests/data/test960
+++ b/tests/data/test960
@@ -22,8 +22,7 @@ smtp
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP without SMTPUTF8 support - UTF-8 based recipient (host part only)
diff --git a/tests/data/test961 b/tests/data/test961
index 2068d8fc84..c52d5df344 100644
--- a/tests/data/test961
+++ b/tests/data/test961
@@ -23,8 +23,7 @@ smtp
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP external VRFY without SMTPUTF8 - UTF-8 recipient (host part only)
diff --git a/tests/data/test962 b/tests/data/test962
index 80292862ba..3f737b65ea 100644
--- a/tests/data/test962
+++ b/tests/data/test962
@@ -23,8 +23,7 @@ IDN
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP without SMTPUTF8 support - UTF-8 based sender (host part only)
diff --git a/tests/data/test963 b/tests/data/test963
index 5d3bae7b56..bce626c5e3 100644
--- a/tests/data/test963
+++ b/tests/data/test963
@@ -23,8 +23,7 @@ IDN
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP without SMTPUTF8 support (IDN) - UTF-8 recipient (host part only)
diff --git a/tests/data/test964 b/tests/data/test964
index 12c312eccd..04e5b1c152 100644
--- a/tests/data/test964
+++ b/tests/data/test964
@@ -24,8 +24,7 @@ IDN
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP external VRFY without SMTPUTF8 (IDN) - UTF-8 recipient (host part)
diff --git a/tests/data/test965 b/tests/data/test965
index 0d29c09849..601db62fe0 100644
--- a/tests/data/test965
+++ b/tests/data/test965
@@ -26,8 +26,7 @@ IDN
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP with SMTPUTF8 support - UTF-8 based sender
diff --git a/tests/data/test966 b/tests/data/test966
index b642e19a9d..646e807589 100644
--- a/tests/data/test966
+++ b/tests/data/test966
@@ -26,8 +26,7 @@ IDN
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP with SMTPUTF8 support - UTF-8 based recipient
diff --git a/tests/data/test967 b/tests/data/test967
index f6e2e32382..7cacbcbdd2 100644
--- a/tests/data/test967
+++ b/tests/data/test967
@@ -30,8 +30,7 @@ IDN
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP external VRFY with SMTPUTF8 support
diff --git a/tests/data/test968 b/tests/data/test968
index 8532c35e7d..4df600483b 100644
--- a/tests/data/test968
+++ b/tests/data/test968
@@ -27,8 +27,7 @@ IDN
 codeset-utf8
 </features>
 <setenv>
-LC_ALL=en_US.UTF-8
-LC_CTYPE=en_US.UTF-8
+LC_ALL=C.UTF-8
 </setenv>
 <name>
 SMTP VRFY with SMTPUTF8 support
diff --git a/tests/runtests.pl b/tests/runtests.pl
index 23736f2ac5..43718fa58b 100755
--- a/tests/runtests.pl
+++ b/tests/runtests.pl
@@ -83,6 +83,7 @@ BEGIN {
 use Digest::MD5 qw(md5);
 use List::Util 'sum';
 use I18N::Langinfo qw(langinfo CODESET);
+use POSIX qw(setlocale LC_ALL);
 
 use serverhelp qw(
     server_exe
@@ -484,6 +485,25 @@ sub parseprotocols {
     push @protocols, 'none';
 }
 
+#######################################################################
+# Check if the operating environment supports UTF-8.
+sub is_utf8_supported {
+    my $result;
+    my $old_LC_ALL;
+    my $was_defined = defined $ENV{'LC_ALL'};
+    if($was_defined) {
+        $old_LC_ALL = $ENV{'LC_ALL'};
+    }
+    setlocale(LC_ALL, $ENV{'LC_ALL'} = "C.UTF-8");
+    $result = lc(langinfo(CODESET())) eq "utf-8";
+    if($was_defined) {
+        $ENV{'LC_ALL'} = $old_LC_ALL;
+    }
+    else {
+        delete $ENV{'LC_ALL'};
+    }
+    return $result;
+}
 
 #######################################################################
 # Check & display information about curl and the host the test suite runs on.
@@ -808,7 +828,7 @@ sub checksystemfeatures {
     # Use this as a proxy for any cryptographic authentication
     $feature{"crypto"} = $feature{"NTLM"} || $feature{"Kerberos"} || $feature{"SPNEGO"};
     $feature{"local-http"} = servers::localhttp();
-    $feature{"codeset-utf8"} = lc(langinfo(CODESET())) eq "utf-8";
+    $feature{"codeset-utf8"} = is_utf8_supported();
     if($feature{"codeset-utf8"}) {
         $ENV{'CURL_TEST_HAVE_CODESET_UTF8'} = 1;
     }